Comments on: Using SQL Where Clauses for Searching

By: 尖锐湿疣

尖锐湿疣 — Sun, 26 Jun 2005 18:19:00 +0000

It’s cool.

By: http://

http:// — Mon, 23 May 2005 13:46:00 +0000

Just to say thanks!! this is a great article and helps keep my queries simple!!

By: http://

http:// — Sun, 08 May 2005 10:27:00 +0000

You say “This is time consuming and doesn’t allow SQL server to optimize your queries” but the alternative limits SQL Server’s ability to optimize the query as well. It would be forced to perform a full table scan on the Customers table rather than using indexes on the columns you’re searching on.

By: Scott Elkin

Scott Elkin — Sat, 07 May 2005 18:21:00 +0000

Actually, if the lastname is null, then '' will be returned as you said. And if @lastname is null, then it will return the third argument, '', in the COALESCE() function. So '' = ''. Remember, COALESCE returns the first non-null value, and '' will never be null.

By: SMR

SMR — Sat, 07 May 2005 16:57:00 +0000

Interesting approach. There seems to be one problem though: What happens if both lastname and @lastname are null. This resolves to ” = NULL which is false, which may give wrong results. I think if you take out the isnull portion (or put it into the coalesce) for the fieldname you will get the results you expect.