0Whenever you want data (columns) to be fetched from more than a single table then think of JOINS in SQL.
It could be 2 or more tables.
*Mostly you join using Primary key and Foreign Key
1) if you want only matching data (rows) from related tables use EQUI JOIN
2) if you want matching and non-matching data (rows) from related tables think of OUTER JOINS
a) LEFT and RIGHT OUTER JOINS basically means from which table you want to fetch NON-MATCHING rows
b) FULL OUTER fetches NON-MATCHING rows from both the TABLES
3) If you want to fetch 2 rows from the same table in a SINGLE select you go in for SELF JOIN
4) Any join between to tables without '=' symbol is called NON-EQUI JOIN.
