1. DB Review

2. Database A database is a collection of data
A database management system (DBMS) is software designed to assist in maintaining and utilizing a large collection of data

3. Why Database is better than a file system
Define the structure:
I/O efficiency
Ability to query(SQL)
High availability
Distributed

4. Relational Database Tables Relationships
Primary Key
Fields (different Types: Int / Boolean / date / file etc..)
Relationships
One to many
Many to one
Many to many
The database is kept on the disk, so anything you create will be there next time you log on.

5. Table ID(PK) Country Name 1 England Yaron Gam 2 USA Kate Omaily 3
Jack Jack

6. Problematic table Prime Minister Country Name Gordon England Yaron Gam
Bush
USA
Kate Omaily
Jack Jack

7. What is the solution Country Name Israel Yaron Gam USA Kate Omaily
There is a One-to-One relationship between Country and Prime minister,
Country
Name
Israel
Yaron Gam
USA
Kate Omaily
Yael Nacsh
Naftali spitzer
Prime Minister
Country
Golda
Israel
Bush
USA

8. Rules of thumb Avoid duplication
One-to-One relationship should be in the same table with other fields.

9. SQL Structured Query Language
is a database computer language designed for the retrieval and management of data in relational database management systems (RDBMS)
Database schema creation
Modification
Database object access control management.

11. Create table The basic format of the CREATE TABLE command is:
CREATE TABLE TableName(
Column1 DataType1 ColConstraint, …
ColumnN DataTypeN ColConstraint,
TableConstraint1, …
TableConstraintM );

12. Example CREATE TABLE Employee( ID INTEGER NOT NULL, Fname VARCHAR(20),
Lname VARCHAR(20),
Gender CHAR(1),
Salary INTEGER NOT NULL,
Dept INTEGER );

13. If you type \d Employee you get:
Column Type Modifiers
id integer not null
fname character varying(20)
lname character varying(20)
gender character(1)
salary integer not null
dept integer

14. Constraints Different types of constraints:
* Not Null * Default Values
* Unique * Primary Key
* Foreign Key * Check Condition

15. Foreign Key Dept Name ManID 12 Sales 988 45 Repair 876 Department ID
FName
LName
Gender
Sallary
Dept
02334
Larry
Bird M
230000 12
04556
Magic
Johnson
270000 45
Foreign Key
Dept
Name
ManID 12
Sales
988 45
Repair
876
Department

16. CREATE TABLE Employee ( ID INTEGER primary key, Fname VARCHAR(20),
Lname VARCHAR(20),
Gender CHAR(1),
Salary INTEGER NOT NULL,
DeptNumber INTEGER REFERENCES Department );
CREATE TABLE Department(
DeptNumber INTEGER PRIMARY KEY,
Name VARCHAR(20),
ManagerId INTEGER );

17. Deleting a table Syntax: DROP TABLE <tableName>;
Mind the order of dropping when there are foreign key constraints.

18. Insert Column Type Modifiers ----------- ------------ ------------
id integer not null
Fname character varying(20)
gender character(1)
deptnumber integer

19. Insert syntax Syntax: insert into tablename (field1,field2…)
values (v1,’v2’,…)
Examples:
insert into employee (id,fname,gender,deptnumber) values(122,'Goldman','M',12);
insert into employee (id,deptnumber) values(123,13);

20. Delete Syntax: DELETE FROM Table WHERE Condition; Example:
DELETE FROM Employee
WHERE id = 121;
WHERE Salary > ;

21. Update Syntax: UPDATE Table SET Field1=value1,,,FieldN=valueN
WHERE Condition
Example:
UPDATE Employee SET Salary = WHERE Salary > ;

22. Queries Syntax: SELECT [Distinct] fields FROM tables WHERE condition
condition: A Boolean condition (For example: age>21, or name=‘Yuval’ ). Only rows which return ‘true’ for this condition will appear in the result
SELECT [Distinct] fields
FROM tables
WHERE condition
ORDER BY field ASC/DESC

23. StudentID
StudentDept.
StudentName
StudentAge
1123
Math
Moshe 25
2245
Computers
Mickey 26
55611
Menahem 29
Select studentID, studentName
From students
Where StudentDept=‘Math’
StudentID
StudentName
1123
Moshe
55611
Menahem

24. The where clause Numerical and string comparison:
!=,<>,=, <, >, >=, <=, between(val1 AND val2)
Logical components: AND, OR
Null verification: IS NULL, IS NOT NULL
Checking against a list with IN, NOT IN.

25. More examples SELECT sname FROM Sailors
WHERE age>=40 AND rating IS NOT NULL ;
SELECT sid, sname
FROM sailors
WHERE sid IN (1223, 2334, 3344) or
sname between(‘George’ and ‘Paul’);
SELECT sid
FROM Sailors
WHERE sname LIKE ‘R%’;

26. How do we compute All sailors who have reserved a boat
sid
sname
rating
age 22 31 58
Dustin
Lubber
Rusty 7 8 10
45.0
55.5
35.0
Reserves
sid
bid
day 22 58
101
103
10/10/96
11/12/96

27. Join Select sname from sailors, reserves
Where sailors.sid=reserves.sid
When there is more than one table in the from
we compute a cross product

28. Stage 1: Sailors x Reserves
sid
sname
rating
age
bid
day 22
Dustin 7
45.0
101
10/10/96 58
103
11/12/96 31
Lubber 8
55.5
Rusty 10
35.0

29. Stage 2: “where sailors.sid=reserves.sid”
sname
rating
age
bid
day 22
Dustin 7
45.0
101
10/10/96 58
103
11/12/96 31
Lubber 8
55.5
Rusty 10
35.0

30. Stage 2: “where sailors.sid=reserves.sid”
sname
rating
age
bid
day 22
Dustin 7
45.0
101
10/10/96 58
Rusty 10
35.0
103
11/12/96

31. Stage 3: “select sname”
Sailors
Reserves
sid
sname
rating
age
bid
day 22
Dustin 7
45.0
101
10/10/96 58
Rusty 10
35.0
103
11/12/96

32. Stage 3: “select sname”
Sailors
sname
Dustin
Rusty
Final answer

33. Order Compute the cross product of the tables
Delete all rows that do not satisfy condition.
Delete all columns that do not appear in fields.
If Distinct is specified eliminate duplicate rows.

34. Aggregation The aggregate operators available in SQL are:
COUNT(*)
COUNT([DISTINCT] A)
SUM([DISTINCT] A)
AVG([DISTINCT] A)
MAX(A)
MIN(A)
SELECT Max(S.age)
FROM Sailors S

35. Nested quires Query inside a query
Select First_Name from Internet_grades where Grade >= (Select Max(Grade) from Infi_grades);