Self Join:

Joining a table to itself is called as self join. Let's see an example- to find the name of each employee's manager. Here we need to join the emp table to itself. For example to find out the manager of a particular employee what you have to do is:
Find out the employee in the emp table by looking the emp-name column.
Get the manager id of that employee by looking at the manager-id column. Let's say the id of the manager is 101. Find out the name of the employee whose employee id is 101.

Example:

To see all the employee along with there manager for whom they work the statement is:

Select worker. emp-name, manager. emp-name
From emp worker , emp manager
Where worker. manager-id =manager .employee-id ;

In the above example , the where clause specifies a condition that is where a manager id of worker table matches the employee id of the manager table .
In the above example the emp table joins to itself. To simulate two table in the from clause there are two aliases, namely worker and manager for the same table emp.



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