Introduction

What is a Join?

SQL Join is a concept of joining two or more tables. In special case, a table can be joined to itself called self-join.

How to Join more than 2 tables at one time?

What are different types of Joins?

SQL (standard) defines 4 types of Joins + 1 special case.

1. Inner (Simple Join)

2. Outer

3. Left (Outer)

4. Right (Outer)

5. Self Join

What is difference between Inner & Outer Join?

Answer

What is Anti Join?

What is Semi Join?

What is Equi Join?

Equi Join is just a name given to Inner Join when the "equal" comparison is done. In case the comparison is different than equal (e.g. <), it is not a Equi join. This term is of importance because the algorithm used for Equi are different from non-Equi once (e.g. Hash Join may not be used for non-Equi Join).