Difference Between This Two Query's

msmiran · September 18th, 2008, 06:45 PM

Hello All,

I write this query for Exercise 2 from Chapter 8 :

Code:

SELECT City, State
FROM MemberDetails AS MD1
WHERE(SELECT COUNT(*) FROM MemberDetails AS MD2 WHERE MD2.City = MD1.City
AND MD2.State = MD1.State) >= 2
AND MD1.City NOT IN (SELECT City FROM Location)
GROUP BY City, State;

And book answer use from Exists Operator :

Code:

SELECT City, State FROM MemberDetails AS MD1
WHERE(SELECT COUNT(*) FROM MemberDetails AS MD2
WHERE NOT EXISTS (SELECT * FROM Location AS L1 WHERE L1.City = MD2.City AND
L1.State = MD2.State)
AND MD1.City = MD2.City AND MD1.State = MD2.State
GROUP BY City,State)>=2
GROUP BY City,State ;

Please comparison this Query's in Speed and etc.

Thanks My Friends.:)