Comments on: How to simulate optional parameters in SQL

By: Frederick Lin : Optional Parameters in SQL

Frederick Lin : Optional Parameters in SQL — Tue, 23 Oct 2007 01:01:47 +0000

[...] certainly be using this more often. I found an article the other day explaining how to simulate optional parameters in SQL without duplicating a single SELECT statement several times, each with a different WHERE [...]

By: Xaprb

Xaprb — Mon, 29 Jan 2007 16:57:22 +0000

There can be. If you enter SMIT% then the database server can do a prefix match, which can use indexes. If you enter %MIT% it becomes a full-length substring search, which is not indexable. So yes, there is always a potential for a bad query to result.

By: Locusta

Locusta — Mon, 29 Jan 2007 16:51:29 +0000

Hello, Is there a performance penalty between these 2 statements:

select * from table1
where (@param1 is null or col1 = @param1)
    and (@param2 is null or col2 = @param2)

select * from table1
where (@param1 is null or col1 like @param1)
    and (@param2 is null or col2 like @param2)

This would allow the user to key in e.g. SMIT% to search for a customer name starting with SMIT, but if he keys in SMITH, then only the exact name would appear in the result list. Is this good practice, or should I avoid? Thanks for this great article!

By: Xaprb

Xaprb — Tue, 15 Aug 2006 11:13:16 +0000

DOH! You are right! I'll amend the article.

By: core

core — Tue, 15 Aug 2006 10:49:31 +0000

Heya,

Shouldn't this:

select * from table1
where (col1 is null or col1 = @param1)
    and (col2 is null or col2 = @param2)

read:

select * from table1
where (@param1 is null or col1 = @param1)
    and (@param2 is null or col2 = @param2)

? Cheers, Will