Schema design is an important part of application development. What are the design goal? What does it include? And what are the pros and cons of each design?

1. liron@gotodba.com
@amitzil
https://gotodba.com
Liron Amitzi

2. Vancouver, BC
Canada

3. Website:
>=Oracle7 (1998)
Since 2009
Since 2020
President
bcoug.org
Senior DB
consultant
(since 2002)
gotodba.com

5. Data Integrity
Store and
retrieve data
Performance
Flexibility

6. Data Types
and Values
Indexes
Constraints and
triggers
Tables and
Normalization

7. ID Low_temp_date Low_temp_C
1 29-DEC-1968 -18
2 22-JAN-1962 7.5
3 1-JAN-9999 -9999
City
Vancouver
Mumbai
Tel Aviv
create table lowest_temp
(id varchar2(10),
city varchar2(100),
low_temp_date varchar2(11),
low_temp_C varchar2(10)
);

8. create table events
(id NUMBER,
year VARCHAR2(10),
month VARCHAR2(10),
day VARCHAR2(10)
);
ID MONTH DAY
1 2020-01 2020-01-01
YEAR
2020

9.  Index type:
◦ B*Tree
◦ Bitmap
◦ Composite - order is important
◦ Function Based Index
 How many?
 Autonomous DB

10. EMPID DEPT CITY
1 IT NY
2 IT SF
3 Sales SF
NAME
Karen
John
Susan
STATE
NY
CA
CA
NAME
IT
Sales
DEPT_ID
10
20
CITY_ID CITY
100 NY
200 SF
STATE
NY
CA
10
10
20
100
200
200

11. 1992 Grover City, CA => Grover Beach, CA
1. UPDATE emp
SET city='Grover Beach'
Where city='Grover City'
AND state='CA';
2. UPDATE cities
SET city='Grover Beach'
Where city='Grover City'
AND state='CA';

12.  Enforce data type and values
 Enforce parent-child relations
 Uniqueness
 Not null
 Triggers - for more complex scenarios

13. OLTP DWH
Saving space Avoid duplicates Allow duplicates
Compress
Data integrity More important Less important
Normalization Normalize De-normalize
Contention Avoid Irrelevant
Performance Instant response Reports

14. Software for "Books and More"
 Books - author, title, date, number of pages, price
 Magazines - publication, title, date, frequency, price
 Audio - musician, title, date, number of tracks, price
How would you model this information?
How many tables will you need?

15. id
type
title
date
price
author (b)
num_pages (b)
publication (m)
frequency (m)
musician (a)
num_tracks (a)
ALL_ITEMS:

16. Very simple
Good performance
 Contention (bad for OLTP)
 Full downtime for any change / problem
 Unnecessary scan of irrelevant data

17. id
type
title
date
price
publication (m)
frequency (m)
id
type
title
date
price
author (b)
num_pages (b)
id
type
title
date
price
musician (a)
num_tracks (a)
BOOKS MAGAZINES AUDIO

18. Simple
Good performance
Access only a relevant product
Changing structure of one product doesn't affect others
Less null columns
 Adding another product
 Querying all products
 Search for an item with unknown type

19. id
author (b)
num_pages (b)
id
type
title
date
price
id
musician (a)
num_tracks (a)
id
publication (m)
frequency (m)
ITEMS
BOOKS
AUDIO
MAGAZINES

20. Classical and straight forward RDBMS design
Simple to summarize common properties
Search for an item with unknown type
 Queries require more joins
 Adding another product

21. id
type
title
date
price
id
prop_name
prop_value
ITEMS
id prop_name
1 author
1 num_pages
prop_value
Stephen King
7000
2 musician Pink
PROPS

22. Amazing flexibility
Adding another product
Entire structure can be changed on the fly
 Enforcing constraints
 Complex with different datatypes
 Have you tried querying it?

23. A specific author:
SELECT * FROM items
WHERE type='book'
AND id IN (SELECT id FROM props
WHERE
prop_name='author' AND
prop_value='Stephen King')

24. A specific author OR number of pages:
SELECT * FROM items
WHERE type='book'
AND id IN (SELECT id FROM props
WHERE (prop_name,prop_value) IN
(('author','Stephen King'),
('num_pages',7000))

25. A specific author AND number of pages:
SELECT * FROM items
WHERE type='book'
AND id IN (SELECT id FROM props
WHERE (prop_name,prop_value) IN
(('author','Stephen King'),
('number_of_pages',7000))
GROUP BY id HAVING count(*)=2)

26. id
type
title
date
price
other_info (JSON)
ALL_ITEMS:
'{
"author" : "Stephen King",
"num_pages" : 7000
}'

27. Easy for developers to handle
Extremely flexible
 Not really RDBMS
 Cannot enforce anything (by definition)

28. A specific author AND number of pages:
SELECT * FROM all_items
WHERE type='book'
AND other_info.author='Stephen King'
AND other_info.num_pages=7000

30. Performance
Flexibility
Data
integrity
Querying
Space

31. Another Crazy Design

32. id
f1
f2
f3
id1
id2
rel_type
f4
f5
OBJECTS RELATIONS
id1 id2
1 3
1 4
rel_type
inheritance
version
2 4 child
4 2 parent

33. Easy for developers and designers (OOP)
Flexible
 Breaks many RDBMS concepts
 Foreign keys
 Query complexity
 Data integrity

34. liron@gotodba.com
@amitzil
https://gotodba.com
Liron Amitzi