Optimizing Sql Query

Select d.NAME, e.NAME
From DEPT d, EMP e
where  d.MGR = e.SS# 

or:

Select  d.NAME, e.NAME 
From EMP e, DEPT d 
where  d.MGR = e.SS# 

Suppose that there are 10 departments and 1000 employees, and that the inner table in each query has an index on the join column. In the first query, the first table produces 10 qualifying rows (in this case, the whole table). In the second query, the first table produces 1000 qualifying rows. The first query will access the EMP table 10 times and scan the DEPT table once. The second query will scan the EMP table once but will access the DEPT table 1000 times. Therefore the first query will perform much better.

 As a rule of thumb, tables should be arranged from smallest effective number rows to largest effective number of rows. The effective row size of a table in a query is obtained by applying the logical conditions that are resolved entirely on that table.