SubQuery

PRINCIPLES
1.(SELECT...)
2.can use with SELECT,FROM,WHERE,HAVING

EX1
SELECT CustTable.CustID, CustTable.balance, (

SELECT SUM( CustTable.balance )
FROM CustTable

), CustTable.balance / ( 
SELECT SUM( CustTable.balance ) 
FROM CustTable ) *100

FROM `custtable`

EX2
SELECT * FROM CustTable WHERE CustTable.Balance >= ( SELECT avg(CustTable.Balance) FROM CustTable );
EX3 SELECT iCityID, sCityName FROM citymaster c where iCityID in(SELECT iStateID FROM statemaster s)