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
select department_id,
count(*) number_of_employees,
avg(salary) avg_salary
from employees
group by department_id
having max(salary) > 2 * min(salary)
Can you
read this
query easily?
If not, please
sit closer

2. ©
Oren
Nakdimon
©
Oren
Nakdimon
https://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
©
Oren
Nakdimon
SQL PL/SQL
Data Model
Concrete Task
General Task
Suggested Solution
Challenges
Variations
“Mini-Patterns”

7. THE DEMO MODEL

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Nakdimon
©
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

10. ©
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Nakdimon
©
Oren
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))
);

11. ©
Oren
Nakdimon
©
Oren
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)

12. ©
Oren
Nakdimon
©
Oren
Nakdimon
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;

13. ©
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Nakdimon
©
Oren
Nakdimon
Find rows that (partially or fully) overlap a given range
Find all the artists that were alive between 2 dates
Get all the projects that were active in the last 7 days
Get the employees that worked in the company during 2019

14. ©
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©
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Nakdimon
Disjoint Ranges

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Nakdimon
Disjoint Ranges
Start1 End1
Start2 End2
Start2>End1

16. ©
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Nakdimon
©
Oren
Nakdimon
Disjoint Ranges
Start1 End1
Start2 End2
Start2>End1
or
Start1>End2

17. ©
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Nakdimon
©
Oren
Nakdimon
Overlapping Ranges
Start1 End1
Start2 End2
Start2<End1
and
Start1<End2

18. ©
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Nakdimon
©
Oren
Nakdimon
Overlapping Ranges
Start1 End1
Start2 End2
Start2<End1
and
Start1<End2

19. ©
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Nakdimon
©
Oren
Nakdimon
Overlapping Ranges
Start1 End1
Start2 End2
Start2<End1
and
Start1<End2

20. ©
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Nakdimon
©
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Nakdimon
The Suggested Solution
StartColumn < EndParameter
and
StartParameter < EndColumn

21. ©
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©
Oren
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

24. ©
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Nakdimon
©
Oren
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

25. ©
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Nakdimon
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Nakdimon
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))
);

26. ©
Oren
Nakdimon
©
Oren
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

27. EXTENDABLE LOV

28. ©
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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
);

29. ©
Oren
Nakdimon
©
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)
);

30. ©
Oren
Nakdimon
©
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

31. ©
Oren
Nakdimon
©
Oren
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;

32. ©
Oren
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;

33. ©
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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.

34. ©
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;

35. ©
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;

36. ©
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;

37. ©
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;

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. ©
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;

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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

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

56. ©
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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
)
/

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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
/

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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;

60. ©
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Pass multiple entities to procedures
Add an album with its songs
➢Related Entities
➢Performance – less roundtrips

61. ©
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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;

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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

64. THE GUARDIAN TRIGGER

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

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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

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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
Complex Validity Check
Logging
Maintaining Denormalized Entities

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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;

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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;

71. 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;

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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;

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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;

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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;

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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;

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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;
/

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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;

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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;

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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;
@trig

80. ©
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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

81. ARC RELATIONSHIP

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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

83. ©
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Implement an arc relationship from Images to Artists and Albums
Implement an arc relationship from a generic entity

84. ©
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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

87. ©
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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

88. ©
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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
);

90. ©
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Nakdimon
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
);

91. ©
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Nakdimon
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
);

92. ©
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Oren
Nakdimon
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
);

93. ©
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Oren
Nakdimon
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
);

94. ©
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©
Oren
Nakdimon
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
);

95. ©
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©
Oren
Nakdimon
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
);

96. ©
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Oren
Nakdimon
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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Nakdimon
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;

98. ©
Oren
Nakdimon
©
Oren
Nakdimon
procedure delete_image(i_id in images.id%type) is
begin
delete images i
where i.id = i_id;
end delete_image;

99. ©
Oren
Nakdimon
©
Oren
Nakdimon
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;

100. ©
Oren
Nakdimon
©
Oren
Nakdimon
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;

101. ©
Oren
Nakdimon
©
Oren
Nakdimon
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;

102. ©
Oren
Nakdimon
©
Oren
Nakdimon
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;

103. THANK YOU☺
Oren Nakdimon
www.db-oriented.com
 oren@db-oriented.com
 +972-54-4393763
@DBoriented