SQL Joins | Oracle SQL joins example

JOINS:

1. The purpose of a join is to combine the data across tables.
2. A join is actually performed by the where clause which combines the specified rows of tables.
3. If a join involves in more than two tables then Oracle joins first two tables based on the joins condition and then compares the result with the next table and so on.

SQL> select * from dept;

DEPTNO	DNAME	LOC
10	INVENTORY	HYBD
20	FINANCE	BGLR
30	HR	MUMBAI

SQL> select * from emp;

EMPNO	ENAME	JOB	MGR	DEPTNO
111	saketh	analyst	444	10
222	sudha	clerk	333	20
333	jagan	manager	111	10
444	madhu	engineer	222	40

Types of Joins:

      1     Equi join

      2     Non-equi join

      3     Self join

      4     Natural join

      5     Cross join

      6     Outer join 

              • Left outer 

              • Right outer 

              • Full outer 

      7     Inner join

      8     Using clause

      9     On clause