>>It's boolean algebra
>>
>>

>>NOT ( A and B) 
>>
>>is
>>
>>NOT(A) or NOT(B)
>>
>>

>>
>>So
>>

>>NOT (Client.NoStatus=@NoStatus AND Client.ModDate<@ModDate)
>>
>>NOT( Client.NoStatus=@NoStatus ) OR NOT(Client.ModDate<@ModDate)
>>
>>is
>>(Client.NoStatus <> @NoStatus) OR ( Client.ModDate>= @ModDate )
>>
>>

>>
>>Also
>>
>>

>>NOT ( A or B)
>>is
>>NOT(A) and NOT(B)
>>

>
>Thanks, this provides valuable information.
>
>If you look at Message #1610467, you will see a more realistic command I have to execute.
>
>Based on your reply, from that referred message, does this mean the second command, the one without the NOT clauses, wouldn't need any parentheses?


I think the second statement needs parentheses. Without, the ANDs will be executed before the ORs

http://msdn.microsoft.com/en-us/library/ms190276.aspx

Your statement

SELECT Client.Numero FROM Client (NOLOCK)
 WHERE (Client.ModDate>=@ModDate OR Client.NoStatus<>@NoStatus) AND
  (Client.ModDate>=@ModDate2 OR Client.NoStatus<>@NoStatus2) AND
  (Client.ModDate>=@ModDate3 OR Client.NoStatus<>@NoStatus3)

without parentheses would be

SELECT Client.Numero FROM Client (NOLOCK)
 WHERE Client.ModDate>=@ModDate OR Client.NoStatus<>@NoStatus AND
  Client.ModDate>=@ModDate2 OR Client.NoStatus<>@NoStatus2 AND
  Client.ModDate>=@ModDate3 OR Client.NoStatus<>@NoStatus3

and is the same as

SELECT Client.Numero FROM Client (NOLOCK)
 WHERE Client.ModDate>=@ModDate 
      OR ( Client.NoStatus<>@NoStatus AND  Client.ModDate>=@ModDate2)
     OR (Client.NoStatus<>@NoStatus2 AND  Client.ModDate>=@ModDate3 )
    OR (Client.NoStatus<>@NoStatus3)

which is different