The document discusses different types of joins in SQL including Cartesian product, natural join, equi join, self join, inner join, left join, right join, and full outer join. It provides examples of each join type using sample tables and describes the key characteristics of each join.

1. JOINS IN SQL
-VARSHA KUMARI

2. content
 Joins:
 Cartesian Product
 Natural Join
 Equi Join
 Self Join
 Inner Join
 outer Join(Left, Right, Full)

3. JOINS
 A JOIN combines together information from two or
more tables into one result set.
 The records from the table are fetched based on
some values that are common to each.
 It can also specifies some condition while
retrieving the data.
 Join = cross product + some condition

4. Cartesian product
 Before understanding JOINS in SQL we
should know about Cartesian Product.
 Also known as Cross Product.

5. Cartesian Product in sets(Mathematics)
 A = { 1, 2, 3} B = { a , b}
 A x B = { (1,a) , (2,a), (3,a), (1, b), (2,b) , (3,b) }

6. Cartesian product
 R1 R2
 R1 x R2
A B
2 E1
4 E2
5 E3
B C
E1 5
E5 7
A B B C
2 E1 E1 5
4 E2 E1 5
5 E3 E1 5
.. .. .. ..

7. Cartesian product
 R1 R2
 R1 x R2
A B
2 E1
4 E2
5 E3
B C
E1 5
E5 7
A B B C
2 E1 E1 5
4 E2 E1 5
5 E3 E1 5
2 E1 E5 7
4 E2 E5 7
5 E3 E5 7

8. Example : Consider two tables

9. Table creation

10. Cartesian product of two table
QUERY: select * from emp2,dept;

12. Cartesian Product :
 Cartesian Product is the all possible combinations
between applied table rows.
 Suppose two tables are T1 and T2
 T1 has r1 rows and c1 columns
 T2 has r2 rows and c2 columns
 Cartesian product of T1 and T2 will have:
 r1 * r2 rows and c1 + c2 columns.

13. Natural Join: Common columns in both the tables
must have same name.
After Natural Join :
 Select * from R1, R2
where R1.B=R2.B;
OR Select *
from R1 natural join R2;
=
A B
2 E1
4 E2
5 E3
B C
E1 5
E2 7
A B B C
2 E1 E1 5
4 E2 E1 5
5 E3 E1 5
2 E1 E2 7
4 E2 E2 7
5 E3 E2 7
A B C
2 E1 5
4 E2 7

14. Natural JOIN:
Select * from Emp2 natural join Dept;
- Behaves Same as Inner Join
- In Natural Join common attribute must have
same name in both the tables

15. Example:
 Select emp_name, loc from Emp2 natural join Dept
where loc= 'NEW YORK';

16. Equi Join
 R1 R2
 After Equi Join :
 Select *from R1,R2
 where R1.B=R2.C;
 or Select *from R1 join R2
 on R1.B=R2.C;
A B
2 E1
4 E2
5 E3
C D
E1 5
E2 7
A B C D
2 E1 E1 5
4 E2 E1 5
5 E3 E1 5
2 E1 E2 7
4 E2 E2 7
5 E3 E2 7
A B C D
2 E1 E1 5
4 E2 E2 7

17. Equi Join:
 Same as inner join , it uses only equality
comparison.
 Query : Select * from Emp2, dept where
emp2.deptno=dept.deptno;

18. Self Join
 A self Join is a type of Join which is used to join a
table to itself. In this join both the columns belongs
to the same table.
 Syntax :
 Select T1.column, T1.column from T1 A inner join T2 B on
A.column= B.column

19. Self Join
 R1
After Equi Join :
Select T.B
from R1 T, R1 S
where T.A=S.A
and T.B <> S.B;
A B
2 E1
2 E2
5 E3
A B A B
2 E1 2 E1
2 E2 2 E1
5 E3 2 E1
2 E1 2 E2
2 E2 2 E2
5 E3 2 E2
2 E1 5 E3
2 E2 5 E3
5 E3 5 E3
B
E2
E1

20. Select * from Emp2 A , Emp2 B
where A.Deptno = B.Deptno;

21. Inner Join
 Inner Join combines the rows retrieved from
multiple tables on the basis of common columns of
the tables.
 It takes that rows from the cartesian product table
where the join elements ( emp.deptno and
dept.deptno in the above query) matches fully
 Syntax:
 Select T1.column, T2.column from T1 inner join T2
on T1.column=T2.column

22. Inner Join
 R1 R2
 After Inner Join
=
A B
2 E1
4 E2
5 E3
B C
E1 5
E2 7
A B B C
2 E1 E1 5
4 E2 E1 5
5 E3 E1 5
2 E1 E2 7
4 E2 E2 7
5 E3 E2 7
A B B C
2 E1 E1 5
4 E2 E2 7

23. Select * from Emp2 inner join Dept on
Emp2.Deptno = Dept.Deptno

24. example
 Select * from Emp2 inner join Dept on
Emp2.Deptno = Dept.Deptno
where loc= 'NEW YORK';

25. Example:
 Select emp_name,loc from Emp2 inner join Dept
on Emp2.Deptno = Dept.Deptno where loc= 'NEW
YORK';

26. Left Outer Join
 Left outer Join takes that rows which are in inner
join output.
 And it also looks for the rows in the left table
which are not in the inner join output.
 The rows are added to the output with null in right
columns.

27. Left Join
 R1 R2
 After Left Join
=
A B
2 E1
4 E2
5 E3
B C
E1 5
E2 7
A B B C
2 E1 E1 5
4 E2 E1 5
5 E3 E1 5
2 E1 E2 7
4 E2 E2 7
5 E3 E2 7
A B B C
2 E1 E1 5
4 E2 E2 7
5 E3 NUL
L
NUL
L

28. Syntax:
 Select T1.column, T2.column from T1 left outer
join T2 on T1.column=T2.column
Eg. Select * from Emp2 left outer join Dept on
Emp2.Deptno = Dept.Deptno;

29. Right Outer Join
 Right outer Join takes that rows which are in inner
join output.
 And it also looks for the rows in the right table
which are not in the inner join output.
 The rows are added to the output with null in left
columns.

30. Right Join
 R1 R2
 After right Join
=
A B
2 E1
4 E2
5 E3
B C
E1 5
E5 7
A B B C
2 E1 E1 5
4 E2 E1 5
5 E3 E1 5
2 E1 E5 7
4 E2 E5 7
5 E3 E5 7
A B B C
2 E1 E1 5
NULL NULL E5 7

31. Syntax:
 Select T1.column, T2.column from T1 right outer
join T2 on T1.column=T2.column
Eg. Select * from Emp2 right outer join Dept on
Emp2.Deptno = Dept.Deptno;

32. Full Outer Join
 Full outer Join takes that rows which are in inner
join output.
 And it also looks for the rows in the left and also
right table which are not in the inner join output.

33. Full Join
 R1 R2
 After Full Join
=
A B
2 E1
4 E2
5 E3
B C
E1 5
E5 7
A B B C
2 E1 E1 5
4 E2 E1 5
5 E3 E1 5
2 E1 E5 7
4 E2 E5 7
5 E3 E5 7
A B B C
2 E1 E1 5
NULL NULL E5 7
4 E2 NULL NULL
5 E3 NULL NULL

34. Syntax:
 Select T1.column, T2.column from T1 full outer
join T2 on T1.column=T2.column
Eg. Select * from Emp2 full outer join Dept on
Emp2.Deptno = Dept.Deptno;

35. Consider two table
Student Faculty
S_id S_name course
1 Amit BCA
2 Ram Btech
3 Hardik BCA
4 Pawan BCA
5 Sumit Btech
6 Aman MCA
7 Hardik BCA
F_Id course Loc
F1 BCA AB 10
F2 Btech AB 1
F3 MTech AB1

36.  Cartesian product:
 Select * from Student, Faculty;
 Natural Join:
 Select * from Student natural join Faculty
 Equi join:
 Select * from student join Faculty on
Student.course=Faculty.course
 Self join:
 Select A.S_name from Student A, Student B where
A.S_id= B.S_id

37.  Inner Join:
 Select Student.S_name from Student inner join
Faculty on Student.course= Faculty.course where
Faculty.loc=‘AB10’
 Left Join:
 Select Student.S_name from Student left outer join
Faculty on Student.course= Faculty.course where
Faculty.loc=‘AB10’
 Right Join:
 Select Student.S_name from Student right outer join
Faculty on Student.course= Faculty.course where
Faculty.loc=‘AB10’