MySQL intersection difference set union

I. MySQL

Only the Union set does not have the keyword of the intersection difference set

Two-Table Structure

A B

Three-Union

3.1 union does not contain duplicate data

 
SelectNameFromAUnionSelectNameFromB;
 

 

3.2 Union all contains duplicate data

Four difference set

Find the ID that exists in Table A but does not exist in Table B

4.1: use Union

 Select ID From  ( --  Union  Select   Distinct A. ID As ID From  A  Union   All  Select   Distinct B. ID As ID From  B)  Temp   Group  By ID Having   Count (ID) =   1 ;

 

4.2:Subquery not in

 
SelectIDFromAWhereIDNot In(SelectIDFromB );
 

4.3:Subquery not exists

SelectIDFromAWhereNot Exists(SelectIDFromBWhereA. ID=B. ID );
 

4.4: left join determines that the right table is null

 
SelectA. IDFromALeft JoinBOnA. ID=B. IDWhereB. IDIs Null Order ByA. ID
 

 

Five intersection intersect:

 Select ID From  (  --  Union  Select   Distinct A. ID As ID From  A  Union   All  Select   Distinct B. ID As IDFrom  B)  Temp   Group   By ID Having   Count (ID) ! =   1 ;