3 Nov 2017

What is join and types of join in sql server


What is join and types of join in SQL server:- 

JOINS:
      A MECHANISM TO COMPARE ONE OR MORE TABLES.


PURPOSE : FOR EASY REPORTING AND DATA GENERATION.


EX: -
             ASSUME ALL PRODUCTS IN ONE TABLE, SALES IN ANOTHER TABLE


A "JOIN" CAN REPORT LIST OF ALL PRODUCTS & THEIR SALES

A "JOIN" CAN REPORT LSIT OF ALL PRODUCTS WITHOU SALES.

TYPES OF JOINS:

1. CROSS JOIN: Used to report all possible combinations

2. INNER JOIN: Used to report only MATCHING data.

3. OUTER JOIN: Used to report MATCHING & MISSING data.

Left Outer Join

Right Outer Join

Full Outer Join

4. SELF JOIN : Used to compare columns within same table.

5.  HASH JOIN : Applicable for tables with unknown size. Dynamic Tables

6.  MERGE JOIN: Applicable for tables with LARGE data. in MBs, GBs

7.  LOOP JOIN: Applicable for tables with SMALL data. in KBs




















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