Few Important Points reg Joins

Qualifying Ambiguous Column Names :

• Use table prefixes to qualify column names that are in multiple tables
• Use table prefixes to improve performance
• Use column aliases to distinguish columns that have identical names but reside in different tables
• Do not use aliases on columns that are identified in the USING clause and listed elsewhere in the SQL statement

Using Table Aliases :

• Use table aliases to simplify queries
• Use table aliases to improve performance

SELECT e.empno, e.ename, d.loc, deptno FROM emp e JOIN dept d USING (deptno) ;