Design Patterns in PL/SQL and SQL

1. Design Patterns
in PL/SQL and SQL
Oren Nakdimon
www.db-oriented.com
 oren@db-oriented.com
 +972-54-4393763
@DBoriented

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Nakdimon
©
Oren
Nakdimon
http://db-oriented.com
Who Am
I?

3. DESIGN PATTERNS
General Definition

4. ©
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Nakdimon
©
Oren
Nakdimon
In software engineering, a software design pattern is a
general, reusable solution to a commonly occurring problem
within a given context in software design. It is not a finished
design that can be transformed directly into source or
machine code. Rather, it is a description or template for how
to solve a problem that can be used in many different
situations. Design patterns are formalized best practices that
the programmer can use to solve common problems when
designing an application or system.
https://en.wikipedia.org/wiki/Software_design_pattern

5. DESIGN PATTERNS
For Oracle Developers

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Nakdimon
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Nakdimon
SQL PL/SQL
Data Model
Concrete Task
General Task
Suggested Solution
Challenges
Variations
“Mini-Patterns”

7. THE DEMO MODEL

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Oren
Nakdimon
ALBUM
# id
* title
* release_date
SONG
# track#
* title
o is_album_favourite
ARTIST
# id
* name
* type
* date_of_birth
o date_of_death
LOV_GENRE
# id
* name

9. OVERLAP CHECK

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create table artists (
id
integer
generated as identity
not null
constraint artists_pk primary key,
name
varchar2(100)
not null,
type
varchar2(6)
not null
constraint artists_type_chk check (type in ('Person','Group')),
date_of_birth
date
not null
constraint artists_dob_chk check (date_of_birth = trunc(date_of_birth)),
date_of_death
date
constraint artists_dod_chk check (date_of_death = trunc(date_of_death))
);

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Nakdimon
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Nakdimon
create table artists (
id
integer
generated as identity
not null
constraint artists_pk primary key,
name
varchar2(100)
not null,
type
varchar2(6)
not null
constraint artists_type_chk check (type in ('Person','Group')),
date_of_birth
date
not null
constraint artists_dob_chk check (date_of_birth = trunc(date_of_birth)),
date_of_death
date
constraint artists_dod_chk check (date_of_death = trunc(date_of_death))
);
Mini-Pattern
Implementing a
“pure” date
attribute (with no
time part)

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Nakdimon
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create or replace package music is
...
procedure get_people
(
i_from_date in date,
i_to_date in date,
o_artists_rc out sys_refcursor
);
...
end music;

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Nakdimon
Find rows that (partially or fully) overlap a given range
Find all the artists that were living between 2 dates

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Nakdimon
Finding Points in a Range is Straightforward

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Nakdimon
procedure get_albums
(
i_released_from in albums.release_date%type,
i_released_to in albums.release_date%type,
o_albums_rc out sys_refcursor
) is
begin
open o_albums_rc for
select al.title,
al.release_date
from albums al
where al.release_date between i_released_from and i_released_to;
end get_albums;

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Nakdimon
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Finding Ranges that Overlap a Range

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Nakdimon
Disjoint Ranges

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Nakdimon
Disjoint Ranges
Start1 End1
Start2 End2
Start2>End1

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©
Oren
Nakdimon
Disjoint Ranges
Start1 End1
Start2 End2
Start2>End1 or Start1>End2

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©
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Nakdimon
Overlapping Ranges
NOT (Start2>End1 or Start1>End2)

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©
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Nakdimon
Overlapping Ranges
NOT (Start2>End1 or Start1>End2)
Start2<End1 and Start1<End2

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Nakdimon
The Suggested Solution
StartColumn < EndParameter
and
StartParameter < EndColumn

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Nakdimon
procedure get_people
(
i_from_date in date,
i_to_date in date,
o_artists_rc out sys_refcursor
) is
begin
open o_artists_rc for
select ar.name,
ar.date_of_birth,
ar.date_of_death
from artists ar
where ar.type = 'Person'
and ar.date_of_birth < i_to_date
and i_from_date < ar.date_of_death
order by ar.date_of_birth,
ar.name;
end get_people;
@over1

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Nakdimon
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Nakdimon
Variation: Inclusive vs. Exclusive Ranges

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Nakdimon
The Suggested Solution
StartColumn < EndParameter
and
StartParameter < EndColumn
StartColumn <= EndParameter
and
StartParameter <= EndColumn
Exclusive
Ranges
Inclusive
Ranges

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Nakdimon
©
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Nakdimon
procedure get_people
(
i_from_date in date,
i_to_date in date,
o_artists_rc out sys_refcursor
) is
begin
open o_artists_rc for
select ar.name,
ar.date_of_birth,
ar.date_of_death
from artists ar
where ar.type = 'Person'
and ar.date_of_birth <= i_to_date
and i_from_date <= ar.date_of_death
order by ar.date_of_birth,
ar.name;
end get_people;
@over2

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Nakdimon
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Variation: Nullable vs. Mandatory Columns
create table artists (
id
integer
generated as identity
not null
constraint artists_pk primary key,
name
varchar2(100)
not null,
type
varchar2(6)
not null
constraint artists_type_chk check (type in ('Person','Band')),
date_of_birth
date
not null
constraint artists_dob_chk check (date_of_birth = trunc(date_of_birth)),
date_of_death
date
constraint artists_dod_chk check (date_of_death = trunc(date_of_death))
);

28. ©
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Nakdimon
©
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Nakdimon
procedure get_people
(
i_from_date in date,
i_to_date in date,
o_artists_rc out sys_refcursor
) is
begin
open o_artists_rc for
select ar.name,
ar.date_of_birth,
ar.date_of_death
from artists ar
where ar.type = 'Person'
and ar.date_of_birth <= i_to_date
and i_from_date <= nvl(ar.date_of_death, date '9999-12-31')
order by ar.date_of_birth,
ar.name;
end get_people;
@over3

29. EXTENDABLE LOV

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Nakdimon
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Nakdimon
create table lov_genres (
id
integer
generated as identity
not null
constraint lov_genres_pk primary key,
name
varchar2(20)
not null
);

31. ©
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©
Oren
Nakdimon
create table albums (
id
integer
generated as identity
not null
constraint albums_pk primary key,
title
varchar2(100)
not null,
release_date
date
not null,
genre_id
constraint albums_fk_genre_id references lov_genres (id)
);
Mini-Pattern
The referencing
column implicitly
gets the data type
of the referenced
column

32. ©
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Nakdimon
©
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Nakdimon
create or replace package music is
...
procedure add_album
(
i_title in albums.title%type,
i_release_date in albums.release_date%type,
i_genre_name in lov_genres.name%type default null,
o_album_id out albums.id%type
); ...
end music;

33. ©
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Nakdimon
©
Oren
Nakdimon
create or replace package body music is
...
procedure add_album
(
i_title in albums.title%type,
i_release_date in albums.release_date%type,
i_genre_name in lov_genres.name%type default null,
o_album_id out albums.id%type
) is
l_genre_id lov_genres.id%type;
begin
l_genre_id := get_genre_id(i_genre_name);
insert into albums
(title,
release_date,
genre_id)
values
(i_title,
i_release_date,
l_genre_id)
returning id into o_album_id;
end add_album;

34. ©
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Nakdimon
©
Oren
Nakdimon
Look-up a reference table and add new values if not exist
Get genre id by its name.
If it doesn’t exist, add it.

35. ©
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©
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Nakdimon
function get_genre_id
(
i_genre_name in lov_genres.name%type,
i_add_if_not_exists in boolean default true
) return lov_genres.id%type
is
l_clean_name lov_genres.name%type :=
initcap(trim(i_genre_name));
l_id lov_genres.id%type;
begin
if i_genre_name is null then
return null;
end if;
begin
select g.id into l_id
from lov_genres g
where g.name = i_genre_name;
exception
when no_data_found then
if i_add_if_not_exists then
begin
insert into lov_genres (name)
values (i_genre_name)
returning id into l_id;
exception
when dup_val_on_index then
l_id := get_genre_id(
i_genre_name => l_clean_name,
i_add_if_not_exists => false);
end;
else
raise_application_error(-20000,
i_genre_name || ' not found');
end if;
end;
return l_id;
end get_genre_id;

36. ©
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Nakdimon
©
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Nakdimon
function get_genre_id
(
i_genre_name in lov_genres.name%type,
i_add_if_not_exists in boolean default true
) return lov_genres.id%type
is
l_clean_name lov_genres.name%type :=
initcap(trim(i_genre_name));
l_id lov_genres.id%type;
begin
if i_genre_name is null then
return null;
end if;
begin
select g.id into l_id
from lov_genres g
where g.name = i_genre_name;
exception
when no_data_found then
if i_add_if_not_exists then
begin
insert into lov_genres (name)
values (i_genre_name)
returning id into l_id;
exception
when dup_val_on_index then
l_id := get_genre_id(
i_genre_name => l_clean_name,
i_add_if_not_exists => false);
end;
else
raise_application_error(-20000,
i_genre_name || ' not found');
end if;
end;
return l_id;
end get_genre_id;

37. ©
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Nakdimon
©
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Nakdimon
function get_genre_id
(
i_genre_name in lov_genres.name%type,
i_add_if_not_exists in boolean default true
) return lov_genres.id%type
is
l_clean_name lov_genres.name%type :=
initcap(trim(i_genre_name));
l_id lov_genres.id%type;
begin
if i_genre_name is null then
return null;
end if;
begin
select g.id into l_id
from lov_genres g
where g.name = i_genre_name;
exception
when no_data_found then
if i_add_if_not_exists then
begin
insert into lov_genres (name)
values (i_genre_name)
returning id into l_id;
exception
when dup_val_on_index then
l_id := get_genre_id(
i_genre_name => l_clean_name,
i_add_if_not_exists => false);
end;
else
raise_application_error(-20000,
i_genre_name || ' not found');
end if;
end;
return l_id;
end get_genre_id;

38. ©
Oren
Nakdimon
©
Oren
Nakdimon
function get_genre_id
(
i_genre_name in lov_genres.name%type,
i_add_if_not_exists in boolean default true
) return lov_genres.id%type
is
l_clean_name lov_genres.name%type :=
initcap(trim(i_genre_name));
l_id lov_genres.id%type;
begin
if i_genre_name is null then
return null;
end if;
begin
select g.id into l_id
from lov_genres g
where g.name = i_genre_name;
exception
when no_data_found then
if i_add_if_not_exists then
begin
insert into lov_genres (name)
values (i_genre_name)
returning id into l_id;
exception
when dup_val_on_index then
l_id := get_genre_id(
i_genre_name => l_clean_name,
i_add_if_not_exists => false);
end;
else
raise_application_error(-20000,
i_genre_name || ' not found');
end if;
end;
return l_id;
end get_genre_id;

39. ©
Oren
Nakdimon
©
Oren
Nakdimon
function get_genre_id
(
i_genre_name in lov_genres.name%type,
i_add_if_not_exists in boolean default true
) return lov_genres.id%type
is
l_clean_name lov_genres.name%type :=
initcap(trim(i_genre_name));
l_id lov_genres.id%type;
begin
if i_genre_name is null then
return null;
end if;
begin
select g.id into l_id
from lov_genres g
where g.name = i_genre_name;
exception
when no_data_found then
if i_add_if_not_exists then
begin
insert into lov_genres (name)
values (i_genre_name)
returning id into l_id;
exception
when dup_val_on_index then
l_id := get_genre_id(
i_genre_name => l_clean_name,
i_add_if_not_exists => false);
end;
else
raise_application_error(-20000,
i_genre_name || ' not found');
end if;
end;
return l_id;
end get_genre_id;

40. ©
Oren
Nakdimon
©
Oren
Nakdimon
function get_genre_id
(
i_genre_name in lov_genres.name%type,
i_add_if_not_exists in boolean default true
) return lov_genres.id%type
is
l_clean_name lov_genres.name%type :=
initcap(trim(i_genre_name));
l_id lov_genres.id%type;
begin
if i_genre_name is null then
return null;
end if;
begin
select g.id into l_id
from lov_genres g
where g.name = i_genre_name;
exception
when no_data_found then
if i_add_if_not_exists then
begin
insert into lov_genres (name)
values (i_genre_name)
returning id into l_id;
exception
when dup_val_on_index then
l_id := get_genre_id(
i_genre_name => l_clean_name,
i_add_if_not_exists => false);
end;
else
raise_application_error(-20000,
i_genre_name || ' not found');
end if;
end;
return l_id;
end get_genre_id;

41. ©
Oren
Nakdimon
©
Oren
Nakdimon
function get_genre_id
(
i_genre_name in lov_genres.name%type,
i_add_if_not_exists in boolean default true
) return lov_genres.id%type
is
l_clean_name lov_genres.name%type :=
initcap(trim(i_genre_name));
l_id lov_genres.id%type;
begin
if i_genre_name is null then
return null;
end if;
begin
select g.id into l_id
from lov_genres g
where g.name = i_genre_name;
exception
when no_data_found then
if i_add_if_not_exists then
begin
insert into lov_genres (name)
values (i_genre_name)
returning id into l_id;
exception
when dup_val_on_index then
l_id := get_genre_id(
i_genre_name => l_clean_name,
i_add_if_not_exists => false);
end;
else
raise_application_error(-20000,
i_genre_name || ' not found');
end if;
end;
return l_id;
end get_genre_id;

42. ©
Oren
Nakdimon
©
Oren
Nakdimon
function get_genre_id
(
i_genre_name in lov_genres.name%type,
i_add_if_not_exists in boolean default true
) return lov_genres.id%type
is
l_clean_name lov_genres.name%type :=
initcap(trim(i_genre_name));
l_id lov_genres.id%type;
begin
if i_genre_name is null then
return null;
end if;
begin
select g.id into l_id
from lov_genres g
where g.name = i_genre_name;
exception
when no_data_found then
if i_add_if_not_exists then
begin
insert into lov_genres (name)
values (i_genre_name)
returning id into l_id;
exception
when dup_val_on_index then
l_id := get_genre_id(
i_genre_name => l_clean_name,
i_add_if_not_exists => false);
end;
else
raise_application_error(-20000,
i_genre_name || ' not found');
end if;
end;
return l_id;
end get_genre_id;

43. ©
Oren
Nakdimon
©
Oren
Nakdimon
function get_genre_id
(
i_genre_name in lov_genres.name%type,
i_add_if_not_exists in boolean default true
) return lov_genres.id%type
is
l_clean_name lov_genres.name%type :=
initcap(trim(i_genre_name));
l_id lov_genres.id%type;
begin
if i_genre_name is null then
return null;
end if;
begin
select g.id into l_id
from lov_genres g
where g.name = i_genre_name;
exception
when no_data_found then
if i_add_if_not_exists then
begin
insert into lov_genres (name)
values (i_genre_name)
returning id into l_id;
exception
when dup_val_on_index then
l_id := get_genre_id(
i_genre_name => l_clean_name,
i_add_if_not_exists => false);
end;
else
raise_application_error(-20000,
i_genre_name || ' not found');
end if;
end;
return l_id;
end get_genre_id;
@lov1

44. ©
Oren
Nakdimon
©
Oren
Nakdimon
Look-up a reference table and add new values if not exist
Get genre id by its name.
If it doesn’t exist, add it.
➢Name Standardization

45. ©
Oren
Nakdimon
©
Oren
Nakdimon
create table lov_genres (
id
integer
generated as identity
not null
constraint lov_genres_pk primary key,
name
varchar2(20)
not null
);
alter table lov_genres add
constraint lov_genres_name_chk check (name = initcap(trim(name)));

46. ©
Oren
Nakdimon
©
Oren
Nakdimon
function get_genre_id
(
i_genre_name in lov_genres.name%type,
i_add_if_not_exists in boolean default true
) return lov_genres.id%type
is
l_clean_name lov_genres.name%type :=
initcap(trim(i_genre_name));
l_id lov_genres.id%type;
begin
if i_genre_name is null then
return null;
end if;
begin
select g.id into l_id
from lov_genres g
where g.name = l_clean_name;
exception
when no_data_found then
if i_add_if_not_exists then
begin
insert into lov_genres (name)
values (l_clean_name)
returning id into l_id;
exception
when dup_val_on_index then
l_id := get_genre_id(
i_genre_name => l_clean_name,
i_add_if_not_exists => false);
end;
else
raise_application_error(-20000,
i_genre_name || ' not found');
end if;
end;
return l_id;
end get_genre_id;
@lov2

47. ©
Oren
Nakdimon
©
Oren
Nakdimon
Look-up a reference table and add new values if not exist
Get genre id by its name.
If it doesn’t exist, add it.
➢Name Standardization
➢Uniqueness

48. ©
Oren
Nakdimon
©
Oren
Nakdimon
create table lov_genres (
id
integer
generated as identity
not null
constraint lov_genres_pk primary key,
name
varchar2(20)
not null
);
alter table lov_genres add
constraint lov_genres_name_chk check (name = initcap(trim(name)));
alter table lov_genres add
constraint lov_genres_name_uk unique (name);
@lov3

49. ©
Oren
Nakdimon
©
Oren
Nakdimon
Look-up a reference table and add new values if not exist
Get genre id by its name.
If it doesn’t exist, add it.
➢Name Standardization
➢Uniqueness
➢Concurrency Control

50. ©
Oren
Nakdimon
©
Oren
Nakdimon
function get_genre_id
(
i_genre_name in lov_genres.name%type,
i_add_if_not_exists in boolean default true
) return lov_genres.id%type
is
l_clean_name lov_genres.name%type :=
initcap(trim(i_genre_name));
l_id lov_genres.id%type;
begin
if i_genre_name is null then
return null;
end if;
begin
select g.id into l_id
from lov_genres g
where g.name = l_clean_name;
exception
when no_data_found then
if i_add_if_not_exists then
begin
insert into lov_genres (name)
values (l_clean_name)
returning id into l_id;
exception
when dup_val_on_index then
l_id := get_genre_id(
i_genre_name => l_clean_name,
i_add_if_not_exists => false);
end;
else
raise_application_error(-20000,
i_genre_name || ' not found');
end if;
end;
return l_id;
end get_genre_id;
@lov4

51. MULTI-VALUE PARAMETERS

52. ©
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©
Oren
Nakdimon
create table songs (
album_id
not null
constraint songs_fk_album_id references albums
on delete cascade,
track#
number(2)
not null,
constraint songs_pk primary key (album_id,track#),
title
varchar2(100)
not null,
artist_id
not null
constraint songs_fk_atrist_id references artists,
is_album_favourite
number(1)
default 0
not null
constraint songs_favourite_boolean_chk check (is_album_favourite in (0,1))
);
create index songs_artist_id_ix on songs (artist_id) compress;

53. ©
Oren
Nakdimon
©
Oren
Nakdimon
create table songs (
album_id
not null
constraint songs_fk_album_id references albums
on delete cascade,
track#
number(2)
not null,
constraint songs_pk primary key (album_id,track#),
title
varchar2(100)
not null,
artist_id
not null
constraint songs_fk_atrist_id references artists,
is_album_favourite
number(1)
default 0
not null
constraint songs_favourite_boolean_chk check (is_album_favourite in (0,1))
);
create index songs_artist_id_ix on songs (artist_id) compress;
Mini-Pattern
Implementing
a Boolean
attribute

54. ©
Oren
Nakdimon
©
Oren
Nakdimon
create table songs (
album_id
not null
constraint songs_fk_album_id references albums
on delete cascade,
track#
number(2)
not null,
constraint songs_pk primary key (album_id,track#),
title
varchar2(100)
not null,
artist_id
not null
constraint songs_fk_atrist_id references artists,
is_album_favourite
number(1)
default 0
not null
constraint songs_favourite_boolean_chk check (is_album_favourite in (0,1))
);
create index songs_artist_id_ix on songs (artist_id) compress;
Mini-Pattern
Implementing
a weak entity

55. ©
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©
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Pass multiple entities to procedures
Add an album with its songs
➢Related Entities

56. ©
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©
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create or replace package music is
...
procedure add_album
(
i_title in albums.title%type,
i_release_date in albums.release_date%type,
i_genre_name in lov_genres.name%type default null,
i_songs in ???,
o_album_id out albums.id%type
);
...
end music;

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create type song_t as object (
track# number(2),
title varchar2(100),
artist_id integer
)
/
create type song_tt as table of song_t
/
create or replace package music is
...
procedure add_album
(
i_title in albums.title%type,
i_release_date in albums.release_date%type,
i_genre_name in lov_genres.name%type default null,
i_songs in song_tt,
o_album_id out albums.id%type
);
...
end music;

58. ©
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©
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Pass multiple entities to procedures
Add an album with its songs
➢Related Entities
➢Performance – less roundtrips

59. ©
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©
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create or replace package body music is
...
procedure add_album
(
i_title in albums.title%type,
i_release_date in albums.release_date%type,
i_genre_name in lov_genres.name%type default null,
o_album_id out albums.id%type
) is
l_genre_id lov_genres.id%type;
begin
l_genre_id := get_genre_id(i_genre_name);
insert into albums
(title,
release_date,
genre_id)
values
(i_title,
i_release_date,
l_genre_id)
returning id into o_album_id;
end add_album;

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procedure add_album
(
i_title in albums.title%type,
i_release_date in albums.release_date%type,
i_genre_name in lov_genres.name%type default null,
i_songs in song_tt,
o_album_id out albums.id%type
) is
l_genre_id lov_genres.id%type;
begin
l_genre_id := get_genre_id(i_genre_name);
insert into albums
(title,
release_date,
genre_id)
values
(i_title,
i_release_date,
l_genre_id)
returning id into o_album_id;
forall i in indices of i_songs
insert into songs
(album_id,
track#,
title,
artist_id)
values
(o_album_id,
i_songs(i).track#,
i_songs(i).title,
i_songs(i).artist_id);
end add_album;

61. ©
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©
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Pass multiple entities to procedures
Add an album with its songs
➢Related Entities
➢Performance – less roundtrips
➢Performance – less context switches
➢Atomicity
@coll1

62. THE GUARDIAN TRIGGER

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Enforce the rule: an album must have at least one song
ALBUM
SONG

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©
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Enforce the rule: an album must have at least one song
ALBUM
SONG

65. ©
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©
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Enforce the rule: an album must have at least one song
ALBUM
SONG

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©
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Enforce the rule: an album must have at least one song
ALBUM
SONG
Whenever some DML is done on some table T,
another piece of code should be executed

67. create or replace package body music is
g_album_songs_integrity_enforced boolean not null := false;
function is_album_songs_integrity_enforced return boolean is
begin
return g_album_songs_integrity_enforced;
end is_album_songs_integrity_enforced;
procedure set_album_songs_integrity_enforced(i_is_enforced in boolean) is
begin
g_album_songs_integrity_enforced := i_is_enforced;
end set_album_songs_integrity_enforced;
...
end music;

68. ©
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create or replace package body music is
g_album_songs_integrity_enforced boolean not null := false;
function is_album_songs_integrity_enforced return boolean is
begin
return g_album_songs_integrity_enforced;
end is_album_songs_integrity_enforced;
procedure set_album_songs_integrity_enforced(i_is_enforced in boolean) is
begin
g_album_songs_integrity_enforced := i_is_enforced;
end set_album_songs_integrity_enforced;
...
end music;

69. ©
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©
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create or replace package body music is
g_album_songs_integrity_enforced boolean not null := false;
function is_album_songs_integrity_enforced return boolean is
begin
return g_album_songs_integrity_enforced;
end is_album_songs_integrity_enforced;
procedure set_album_songs_integrity_enforced(i_is_enforced in boolean) is
begin
g_album_songs_integrity_enforced := i_is_enforced;
end set_album_songs_integrity_enforced;
...
end music;

70. ©
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©
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create or replace package body music is
g_album_songs_integrity_enforced boolean not null := false;
function is_album_songs_integrity_enforced return boolean is
begin
return g_album_songs_integrity_enforced;
end is_album_songs_integrity_enforced;
procedure set_album_songs_integrity_enforced(i_is_enforced in boolean) is
begin
g_album_songs_integrity_enforced := i_is_enforced;
end set_album_songs_integrity_enforced;
...
end music;

71. ©
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©
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create or replace package body music is
g_album_songs_integrity_enforced boolean not null := false;
function is_album_songs_integrity_enforced return boolean is
begin
return g_album_songs_integrity_enforced;
end is_album_songs_integrity_enforced;
procedure set_album_songs_integrity_enforced(i_is_enforced in boolean) is
begin
g_album_songs_integrity_enforced := i_is_enforced;
end set_album_songs_integrity_enforced;
...
end music;
create or replace package music is
function is_album_songs_integrity_enforced return Boolean;
...
end music;

72. ©
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create or replace trigger albums_guardian_trigger
before insert on albums
begin
if not music.is_album_songs_integrity_enforced then
raise_application_error(
-20000,
'to maintain albums and songs, please use the procedures in the music package');
end if;
end albums_guardian_trigger;
/
create or replace trigger songs_guardian_trigger
before delete or update of album_id on songs
begin
if not music.is_album_songs_integrity_enforced then
raise_application_error(
-20000,
'to maintain albums and songs, please use the procedures in the music package');
end if;
end songs_guardian_trigger;
/

73. ©
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©
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procedure add_album (
i_title in albums.title%type,
i_release_date in albums.release_date%type,
i_genre_name in lov_genres.name%type default null,
i_songs in song_tt,
o_album_id out albums.id%type)
is
l_genre_id lov_genres.id%type;
begin
if i_songs is null or i_songs is empty then
raise_application_error(
-20000, 'an album must have songs');
end if;
l_genre_id := get_genre_id(i_genre_name);
set_album_songs_integrity_enforced(true);
insert into albums (title, release_date, genre_id)
values (i_title, i_release_date, l_genre_id)
returning id into o_album_id;
forall i in indices of i_songs
insert into songs
(album_id,
track#,
title,
artist_id)
values
(o_album_id,
i_songs(i).track#,
i_songs(i).title,
i_songs(i).artist_id);
set_album_songs_integrity_enforced
(false);
exception
when others then
set_album_songs_integrity_enforced
(false);
raise;
end add_album;

74. ©
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©
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procedure add_album (
i_title in albums.title%type,
i_release_date in albums.release_date%type,
i_genre_name in lov_genres.name%type default null,
i_songs in song_tt,
o_album_id out albums.id%type)
is
l_genre_id lov_genres.id%type;
begin
if i_songs is null or i_songs is empty then
raise_application_error(
-20000, 'an album must have songs');
end if;
l_genre_id := get_genre_id(i_genre_name);
set_album_songs_integrity_enforced(true);
insert into albums (title, release_date, genre_id)
values (i_title, i_release_date, l_genre_id)
returning id into o_album_id;
forall i in indices of i_songs
insert into songs
(album_id,
track#,
title,
artist_id)
values
(o_album_id,
i_songs(i).track#,
i_songs(i).title,
i_songs(i).artist_id);
set_album_songs_integrity_enforced
(false);
exception
when others then
set_album_songs_integrity_enforced
(false);
raise;
end add_album;

75. ©
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©
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Nakdimon
procedure add_album (
i_title in albums.title%type,
i_release_date in albums.release_date%type,
i_genre_name in lov_genres.name%type default null,
i_songs in song_tt,
o_album_id out albums.id%type)
is
l_genre_id lov_genres.id%type;
begin
if i_songs is null or i_songs is empty then
raise_application_error(
-20000, 'an album must have songs');
end if;
l_genre_id := get_genre_id(i_genre_name);
set_album_songs_integrity_enforced(true);
insert into albums (title, release_date, genre_id)
values (i_title, i_release_date, l_genre_id)
returning id into o_album_id;
forall i in indices of i_songs
insert into songs
(album_id,
track#,
title,
artist_id)
values
(o_album_id,
i_songs(i).track#,
i_songs(i).title,
i_songs(i).artist_id);
set_album_songs_integrity_enforced
(false);
exception
when others then
set_album_songs_integrity_enforced
(false);
raise;
end add_album;

76. ©
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©
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Nakdimon
procedure add_album (
i_title in albums.title%type,
i_release_date in albums.release_date%type,
i_genre_name in lov_genres.name%type default null,
i_songs in song_tt,
o_album_id out albums.id%type)
is
l_genre_id lov_genres.id%type;
begin
if i_songs is null or i_songs is empty then
raise_application_error(
-20000, 'an album must have songs');
end if;
l_genre_id := get_genre_id(i_genre_name);
set_album_songs_integrity_enforced(true);
insert into albums (title, release_date, genre_id)
values (i_title, i_release_date, l_genre_id)
returning id into o_album_id;
forall i in indices of i_songs
insert into songs
(album_id,
track#,
title,
artist_id)
values
(o_album_id,
i_songs(i).track#,
i_songs(i).title,
i_songs(i).artist_id);
set_album_songs_integrity_enforced
(false);
exception
when others then
set_album_songs_integrity_enforced
(false);
raise;
end add_album;
@trig

77. ©
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©
Oren
Nakdimon
The Suggested Solution
 Put the logic in a procedure (or procedures)
 Use a global variable that indicates if the DML is allowed
 Initialize it to FALSE
 Set it to TRUE only for the duration of the procedure
 A statement-level trigger on the DML verifies the flag is on

78. CONDITIONAL UNIQUENESS

79. ©
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procedure set_album_favourite_song
(
i_album_id in songs.album_id%type,
i_track# in songs.track#%type,
i_is_favourite in songs.is_album_favourite%type
) is
begin
update songs s
set s.is_album_favourite = i_is_favourite
where s.album_id = i_album_id
and s.track# = i_track#;
end set_album_favourite_song;
@cond1

80. ©
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Enforce the rule: each album may have at most one favourite song
Enforce a business rule that requires uniqueness of an attribute
(column) within a subset of the entity instances (table rows)

81. ©
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©
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Nakdimon
The Suggested Solution
 Create a virtual column that has NULLs for the non-relevant rows
 Create a unique constraint on the virtual column
alter table songs add (
favourite_song_of_album_id as (decode(is_album_favourite,1,album_id)) virtual
constraint songs_favourite_uk unique
);

82. ©
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Nakdimon
©
Oren
Nakdimon
The Suggested Solution
 Create a virtual column that has NULLs for the non-relevant rows
 Create a unique constraint on the virtual column
alter table songs add (
favourite_song_of_album_id as (decode(is_album_favourite,1,album_id)) virtual
constraint songs_favourite_uk unique
);

83. ©
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Nakdimon
©
Oren
Nakdimon
The Suggested Solution
 Create a virtual column that has NULLs for the non-relevant rows
 Create a unique constraint on the virtual column
alter table songs add (
favourite_song_of_album_id as (decode(is_album_favourite,1,album_id)) virtual
constraint songs_favourite_uk unique
);
@cond2

84. ©
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©
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procedure unset_album_favourite_song(i_album_id in songs.album_id%type) is
begin
update songs s
set s.is_album_favourite = 0
where s.favourite_song_of_album_id = i_album_id;
end unset_album_favourite_song;

85. ©
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©
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Nakdimon
procedure unset_album_favourite_song(i_album_id in songs.album_id%type) is
begin
update songs s
set s.is_album_favourite = 0
where s.favourite_song_of_album_id = i_album_id;
end unset_album_favourite_song;
-----------------------------------------------------------
| Id | Operation | Name |
-----------------------------------------------------------
| 0 | UPDATE STATEMENT | |
| 1 | UPDATE | SONGS |
| 2 | TABLE ACCESS BY INDEX ROWID| SONGS |
|* 3 | INDEX UNIQUE SCAN | SONGS_FAVOURITE_UK |
-----------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("S"."FAVOURITE_SONG_OF_ALBUM_ID"=TO_NUMBER(:I_ALBUM_ID))

86. ©
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procedure unset_album_favourite_song(i_album_id in songs.album_id%type) is
begin
update songs s
set s.is_album_favourite = 0
where s.favourite_song_of_album_id = i_album_id;
end unset_album_favourite_song;
-----------------------------------------------------------
| Id | Operation | Name |
-----------------------------------------------------------
| 0 | UPDATE STATEMENT | |
| 1 | UPDATE | SONGS |
| 2 | TABLE ACCESS BY INDEX ROWID| SONGS |
|* 3 | INDEX UNIQUE SCAN | SONGS_FAVOURITE_UK |
-----------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("S"."FAVOURITE_SONG_OF_ALBUM_ID"=TO_NUMBER(:I_ALBUM_ID))

87. ©
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©
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Nakdimon
procedure unset_album_favourite_song(i_album_id in songs.album_id%type) is
begin
update songs s
set s.is_album_favourite = 0
where s.favourite_song_of_album_id = i_album_id;
end unset_album_favourite_song;
procedure set_album_favourite_song
(
i_album_id in songs.album_id%type,
i_track# in songs.track#%type
) is
begin
unset_album_favourite_song(i_album_id => i_album_id);
update songs s
set s.is_album_favourite = 1
where s.album_id = i_album_id
and s.track# = i_track#;
end set_album_favourite_song;

88. ©
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©
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Nakdimon
procedure unset_album_favourite_song(i_album_id in songs.album_id%type) is
begin
update songs s
set s.is_album_favourite = 0
where s.favourite_song_of_album_id = i_album_id;
end unset_album_favourite_song;
procedure set_album_favourite_song
(
i_album_id in songs.album_id%type,
i_track# in songs.track#%type
) is
begin
unset_album_favourite_song(i_album_id => i_album_id);
update songs s
set s.is_album_favourite = 1
where s.album_id = i_album_id
and s.track# = i_track#;
end set_album_favourite_song;

89. ©
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Nakdimon
©
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Nakdimon
procedure unset_album_favourite_song(i_album_id in songs.album_id%type) is
begin
update songs s
set s.is_album_favourite = 0
where s.favourite_song_of_album_id = i_album_id;
end unset_album_favourite_song;
procedure set_album_favourite_song
(
i_album_id in songs.album_id%type,
i_track# in songs.track#%type
) is
begin
unset_album_favourite_song(i_album_id => i_album_id);
update songs s
set s.is_album_favourite = 1
where s.album_id = i_album_id
and s.track# = i_track#;
end set_album_favourite_song;

90. CORRELATED RESULTS

91. ©
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©
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Return albums – and all their songs – based on various inputs

92. ©
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©
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Nakdimon
Return albums – and all their songs – based on various inputs
procedure get_albums
(
i_artist_name in artists.name%type default null,
i_genre_id_list in int_tt default null,
i_released_after in albums.release_date%type default null,
i_released_before in albums.release_date%type default null,
o_albums_rc out sys_refcursor,
o_songs_rc out sys_refcursor
);

93. ©
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©
Oren
Nakdimon
Return albums – and all their songs – based on various inputs
procedure get_albums
(
i_artist_name in artists.name%type default null,
i_genre_id_list in int_tt default null,
i_released_after in albums.release_date%type default null,
i_released_before in albums.release_date%type default null,
o_albums_rc out sys_refcursor,
o_songs_rc out sys_refcursor
);
create type int_tt as table of integer

94. ©
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Nakdimon
©
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Nakdimon
Return albums – and all their songs – based on various inputs
procedure get_albums
(
i_artist_name in artists.name%type default null,
i_genre_id_list in int_tt default null,
i_released_after in albums.release_date%type default null,
i_released_before in albums.release_date%type default null,
o_albums_rc out sys_refcursor,
o_songs_rc out sys_refcursor
);

95. ©
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Nakdimon
©
Oren
Nakdimon
Return albums – and all their songs – based on various inputs
procedure get_albums
(
i_artist_name in artists.name%type default null,
i_genre_id_list in int_tt default null,
i_released_after in albums.release_date%type default null,
i_released_before in albums.release_date%type default null,
o_albums_rc out sys_refcursor,
o_songs_rc out sys_refcursor
);

96. procedure get_albums (
i_artist_name in artists.name%type default null,
i_genre_id_list in int_tt default null,
i_released_after in albums.release_date%type default null,
i_released_before in albums.release_date%type default null,
o_albums_rc out sys_refcursor,
o_songs_rc out sys_refcursor)
is
begin
open o_albums_rc for
select al.id,
al.title,
al.release_date,
al.genre_id
from albums al
where ......................
order by al.id;
open o_songs_rc for
select s.album_id,
s.track#,
s.title,
s.artist_id,
s.is_album_favourite
from albums al,
songs s
where ......................
and s.album_id = al.id
order by s.album_id,
s.track#;
end get_albums;

97. ©
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Nakdimon
©
Oren
Nakdimon
procedure get_albums (
i_artist_name in artists.name%type default null,
i_genre_id_list in int_tt default null,
i_released_after in albums.release_date%type default null,
i_released_before in albums.release_date%type default null,
o_albums_rc out sys_refcursor,
o_songs_rc out sys_refcursor)
is
pragma autonomous_transaction;
l_album_id_list int_tt;
begin
set transaction read only;
select al.id
bulk collect into l_album_id_list
from albums al
where (i_artist_name is null or
exists (select null from songs s, artists ar
where s.album_id = al.id
and instr(ar.name, i_artist_name) > 0
and s.artist_id = ar.id))
and (i_genre_id_list is null or al.genre_id member of i_genre_id_list)
and al.release_date >= nvl(i_released_after, date '0001-01-01')
and al.release_date <= nvl(i_released_before, date '9999-12-31');

98. ©
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Nakdimon
©
Oren
Nakdimon
procedure get_albums (
i_artist_name in artists.name%type default null,
i_genre_id_list in int_tt default null,
i_released_after in albums.release_date%type default null,
i_released_before in albums.release_date%type default null,
o_albums_rc out sys_refcursor,
o_songs_rc out sys_refcursor)
is
pragma autonomous_transaction;
l_album_id_list int_tt;
begin
set transaction read only;
select al.id
bulk collect into l_album_id_list
from albums al
where (i_artist_name is null or
exists (select null from songs s, artists ar
where s.album_id = al.id
and instr(ar.name, i_artist_name) > 0
and s.artist_id = ar.id))
and (i_genre_id_list is null or al.genre_id member of i_genre_id_list)
and al.release_date >= nvl(i_released_after, date '0001-01-01')
and al.release_date <= nvl(i_released_before, date '9999-12-31');

99. ©
Oren
Nakdimon
©
Oren
Nakdimon
procedure get_albums (
i_artist_name in artists.name%type default null,
i_genre_id_list in int_tt default null,
i_released_after in albums.release_date%type default null,
i_released_before in albums.release_date%type default null,
o_albums_rc out sys_refcursor,
o_songs_rc out sys_refcursor)
is
pragma autonomous_transaction;
l_album_id_list int_tt;
begin
set transaction read only;
select al.id
bulk collect into l_album_id_list
from albums al
where (i_artist_name is null or
exists (select null from songs s, artists ar
where s.album_id = al.id
and instr(ar.name, i_artist_name) > 0
and s.artist_id = ar.id))
and (i_genre_id_list is null or al.genre_id member of i_genre_id_list)
and al.release_date >= nvl(i_released_after, date '0001-01-01')
and al.release_date <= nvl(i_released_before, date '9999-12-31');
open o_albums_rc for
select a.id, a.title, a.release_date, a.genre_id
from table(l_album_id_list) c,
albums a
where a.id = c.column_value
order by a.id;
open o_songs_rc for
select s.album_id, s.track#, s.title, s.artist_id,
s.is_album_favourite
from table(l_album_id_list) c,
songs s
where s.album_id = c.column_value
order by s.album_id,
s.track#;
commit;
end get_albums;

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procedure get_albums (
i_artist_name in artists.name%type default null,
i_genre_id_list in int_tt default null,
i_released_after in albums.release_date%type default null,
i_released_before in albums.release_date%type default null,
o_albums_rc out sys_refcursor,
o_songs_rc out sys_refcursor)
is
pragma autonomous_transaction;
l_album_id_list int_tt;
begin
set transaction read only;
select al.id
bulk collect into l_album_id_list
from albums al
where (i_artist_name is null or
exists (select null from songs s, artists ar
where s.album_id = al.id
and instr(ar.name, i_artist_name) > 0
and s.artist_id = ar.id))
and (i_genre_id_list is null or al.genre_id member of i_genre_id_list)
and al.release_date >= nvl(i_released_after, date '0001-01-01')
and al.release_date <= nvl(i_released_before, date '9999-12-31');
open o_albums_rc for
select a.id, a.title, a.release_date, a.genre_id
from table(l_album_id_list) c,
albums a
where a.id = c.column_value
order by a.id;
open o_songs_rc for
select s.album_id, s.track#, s.title, s.artist_id,
s.is_album_favourite
from table(l_album_id_list) c,
songs s
where s.album_id = c.column_value
order by s.album_id,
s.track#;
commit;
end get_albums;

101. ARC RELATIONSHIP

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Implement an arc relationship from Images to Artists and Albums
Implement an arc relationship from a generic entity

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ALBUM
# id
* title
* release_date
SONG
# track#
* title
o is_album_favourite
ARTIST
# id
* name
* type
* date_of_birth
o date_of_death
LOV_GENRE
# id
* name
IMAGE
# id
* name
* size
* resolution

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Option #1 – Multiple Dedicated Tables
ALBUM_IMAGES
# image_id
* album_id (FK)
* name
* size
* resolution
.
.
.
ARTIST_IMAGES
# image_id
* artist_id (FK)
* name
* size
* resolution
.
.
.
?_IMAGES
# image_id
* ?_id (FK)
* name
* size
* resolution
.
.
.
Code Code Code

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Option #2 – A Single Table with Dedicated Columns
IMAGES
# image_id
o album_id (FK)
o artist_id (FK)
* name
* size
* resolution
.
.
.
CHECK
(album_id is null and artist_id is not null
or
album_id is not null and artist_id is null)

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CHECK
(nvl2(album_id,1,0)+nvl2(artist_id,1,0)=1)
Option #2 – A Single Table with Dedicated Columns
IMAGES
# image_id
o album_id (FK)
o artist_id (FK)
* name
* size
* resolution
.
.
.
Code
album/artist

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Option #3 – A Generic Table
IMAGES
# image_id
o owner_type
o owner_id
* name
* size
* resolution
.
.
.
Code
check (owner_type in ('Artist','Album'))
No Referential Integrity

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The Suggested Solution – Option #4
 The generic table solution (option #3)
 + virtual columns to enforce referential integrity

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create table images (
id
integer generated as identity not null constraint images_pk primary key,
name
varchar2(200) not null,
size_in_bytes
integer not null,
resolution
integer not null,
--- ...
owner_type
varchar2(6) not null
constraint images_owner_type_chk check (owner_type in ('Artist','Album')),
owner_id
integer not null,
artist_id
invisible
generated always as (decode(owner_type,'Artist',owner_id)) virtual
constraint images_fk_artist_id references artists(id) on delete cascade,
album_id
invisible
generated always as (decode(owner_type,'Album',owner_id)) virtual
constraint images_fk_album_id references albums(id) on delete cascade
);

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create table images (
id
integer generated as identity not null constraint images_pk primary key,
name
varchar2(200) not null,
size_in_bytes
integer not null,
resolution
integer not null,
--- ...
owner_type
varchar2(6) not null
constraint images_owner_type_chk check (owner_type in ('Artist','Album')),
owner_id
integer not null,
artist_id
invisible
generated always as (decode(owner_type,'Artist',owner_id)) virtual
constraint images_fk_artist_id references artists(id) on delete cascade,
album_id
invisible
generated always as (decode(owner_type,'Album',owner_id)) virtual
constraint images_fk_album_id references albums(id) on delete cascade
);

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create table images (
id
integer generated as identity not null constraint images_pk primary key,
name
varchar2(200) not null,
size_in_bytes
integer not null,
resolution
integer not null,
--- ...
owner_type
varchar2(6) not null
constraint images_owner_type_chk check (owner_type in ('Artist','Album')),
owner_id
integer not null,
artist_id
invisible
generated always as (decode(owner_type,'Artist',owner_id)) virtual
constraint images_fk_artist_id references artists(id) on delete cascade,
album_id
invisible
generated always as (decode(owner_type,'Album',owner_id)) virtual
constraint images_fk_album_id references albums(id) on delete cascade
);

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create table images (
id
integer generated as identity not null constraint images_pk primary key,
name
varchar2(200) not null,
size_in_bytes
integer not null,
resolution
integer not null,
--- ...
owner_type
varchar2(6) not null
constraint images_owner_type_chk check (owner_type in ('Artist','Album')),
owner_id
integer not null,
artist_id
invisible
generated always as (decode(owner_type,'Artist',owner_id)) virtual
constraint images_fk_artist_id references artists(id) on delete cascade,
album_id
invisible
generated always as (decode(owner_type,'Album',owner_id)) virtual
constraint images_fk_album_id references albums(id) on delete cascade
);

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create table images (
id
integer generated as identity not null constraint images_pk primary key,
name
varchar2(200) not null,
size_in_bytes
integer not null,
resolution
integer not null,
--- ...
owner_type
varchar2(6) not null
constraint images_owner_type_chk check (owner_type in ('Artist','Album')),
owner_id
integer not null,
artist_id
invisible
generated always as (decode(owner_type,'Artist',owner_id)) virtual
constraint images_fk_artist_id references artists(id) on delete cascade,
album_id
invisible
generated always as (decode(owner_type,'Album',owner_id)) virtual
constraint images_fk_album_id references albums(id) on delete cascade
);

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create table images (
id
integer generated as identity not null constraint images_pk primary key,
name
varchar2(200) not null,
size_in_bytes
integer not null,
resolution
integer not null,
--- ...
owner_type
varchar2(6) not null
constraint images_owner_type_chk check (owner_type in ('Artist','Album')),
owner_id
integer not null,
artist_id
invisible
generated always as (decode(owner_type,'Artist',owner_id)) virtual
constraint images_fk_artist_id references artists(id) on delete cascade,
album_id
invisible
generated always as (decode(owner_type,'Album',owner_id)) virtual
constraint images_fk_album_id references albums(id) on delete cascade
);

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create table images (
id
integer generated as identity not null constraint images_pk primary key,
name
varchar2(200) not null,
size_in_bytes
integer not null,
resolution
integer not null,
--- ...
owner_type
varchar2(6) not null
constraint images_owner_type_chk check (owner_type in ('Artist','Album')),
owner_id
integer not null,
artist_id
invisible
generated always as (decode(owner_type,'Artist',owner_id)) virtual
constraint images_fk_artist_id references artists(id) on delete cascade,
album_id
invisible
generated always as (decode(owner_type,'Album',owner_id)) virtual
constraint images_fk_album_id references albums(id) on delete cascade
);

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create or replace package images_dl is
procedure add_image
(
i_owner_type in images.owner_type%type,
i_owner_id in images.owner_id%type,
i_name in images.name%type,
i_size in images.size_in_bytes%type,
i_resolution in images.resolution%type,
o_id out images.id%type
);
procedure delete_image(i_id in images.id%type);
procedure get_images
(
i_owner_type in images.owner_type%type,
i_owner_id in images.owner_id%type,
o_images_rc out sys_refcursor
);
end images_dl;

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procedure add_image
(
i_owner_type in images.owner_type%type,
i_owner_id in images.owner_id%type,
i_name in images.name%type,
i_size in images.size_in_bytes%type,
i_resolution in images.resolution%type,
o_id out images.id%type
) is
begin
insert into images
(name,
size_in_bytes,
resolution,
owner_type,
owner_id)
values
(i_name,
i_size,
i_resolution,
i_owner_type,
i_owner_id)
returning id into o_id;
end add_image;

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procedure delete_image(i_id in images.id%type) is
begin
delete images i
where i.id = i_id;
end delete_image;

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procedure get_images
(
i_owner_type in images.owner_type%type,
i_owner_id in images.owner_id%type,
o_images_rc out sys_refcursor
) is
begin
open o_images_rc for
select i.owner_id,
i.id,
i.name,
i.size_in_bytes,
i.resolution
from images i
where i.owner_type = i_owner_type
and i.owner_id = i_owner_id
order by i.id;
end get_images;

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create or replace package music is
...
procedure get_artist
(
i_id in artists.id%type,
o_name out artists.name%type,
o_type out artists.type%type,
o_date_of_birth out artists.date_of_birth%type,
o_date_of_death out artists.date_of_death%type,
o_images_rc out sys_refcursor
);
procedure get_album
(
i_id in albums.id%type,
o_title out albums.title%type,
o_songs_rc out sys_refcursor,
o_images_rc out sys_refcursor
);
...
end music;

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procedure get_artist
(
i_id in artists.id%type,
o_name out artists.name%type,
o_type out artists.type%type,
o_date_of_birth out artists.date_of_birth%type,
o_date_of_death out artists.date_of_death%type,
o_images_rc out sys_refcursor
) is
begin
select ar.name,
ar.type,
ar.date_of_birth,
ar.date_of_death
into o_name,
o_type,
o_date_of_birth,
o_date_of_death
from artists ar
where ar.id = i_id;
images_dl.get_images(i_owner_type => 'Artist',
i_owner_id => i_id,
o_images_rc => o_images_rc);
end get_artist;

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procedure get_album
(
i_id in albums.id%type,
o_title out albums.title%type,
o_songs_rc out sys_refcursor,
o_images_rc out sys_refcursor
) is
begin
select al.title into o_title
from albums al
where al.id = i_id;
open o_songs_rc for
select s.album_id, s.track#, s.title, s.artist_id, s.is_album_favourite
from songs s
where s.album_id = i_id
order by s.track#;
images_dl.get_images(i_owner_type => 'Album',
i_owner_id => i_id,
o_images_rc => o_images_rc);
end get_album;