SQL : Difference Between Union and Union All (Set Operators)

 

 

Union:

 

The Set operator Union, will combine the results of first query and second query, but it doesnt displays the

 

records common to both the queries..

 

 

 Union :  ( Records of Query 1 + Records Of Query 2) - (Records common to both the queries)

 

Usage : (Query 1 ) Union (Query 2)

 

Union All :

 

The Set operator Union, will combine the results of first query and second query, and records common to both the queries..

 

 Union All :  ( Records of Query 1 + Records Of Query 2) + (Records common to both the queries)

 

 Usage : (Query 1 ) Union all (Query 2)

 

Note : The rules of Set operators are..

 

   The number of colums and datatypes of coloums (not colum names ) returned by the query 1 should be same with the number of coloums retrived by the query two.