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POProper way to handle 'optional' where clause filters in SQL?
 

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  1. POProper way to handle 'optional' where clause filters in SQL?
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    <p>Let's say you have a stored procedure, and it takes an optional parameter. You want to use this optional parameter in the SQL query. Typically this is how I've seen it done:</p> <pre><code>SELECT * FROM dbo.MyTableName t1 WHERE t1.ThisField = 'test' AND (@MyOptionalParam IS NULL OR t1.MyField = @MyOptionalParam) </code></pre> <p>This seems to work well, however it causes a high amount of logical reads if you run the query with STATISTICS IO ON. I've also tried the following variant:</p> <pre><code>SELECT * FROM dbo.MyTableName t1 WHERE t1.ThisField = 'test' AND t1.MyField = CASE WHEN @MyOptionalParam IS NULL THEN t1.MyField ELSE @MyOptionalParam END </code></pre> <p>And it yields the same number of high reads. If we convert the SQL to a string, then call sp_ExecuteSQL on it, the reads are almost nil:</p> <pre><code>DECLARE @sql nvarchar(max) SELECT @sql = 'SELECT * FROM dbo.MyTableName t1 WHERE t1.ThisField = ''test''' IF @MyOptionalParam IS NOT NULL BEGIN SELECT @sql = @sql + ' AND t1.MyField = @MyOptionalParam ' END EXECUTE sp_ExecuteSQL @sql, N'@MyOptionalParam', @MyOptionalParam </code></pre> <p>Am I crazy? Why are optional where clauses so hard to get right?</p> <p><strong>Update:</strong> I'm basically asking if there's a way to keep the standard syntax inside of a stored procedure and get low logical reads, like the sp_ExecuteSql method does. It seems completely crazy to me to build up a string... not to mention it makes it harder to maintain, debug, visualize..</p>
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    1. CONicholas, see the union approach below for a way to use standard sql syntax without dynamic sql - I'd be very curious to see you post on how it performs in your scenario...
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    2. CO@Nicholas: Constructing a query as a string before executing it is **exactly** what *dynamic* SQL is. It's a minor issue to debug - copy/paste, get rid of string concatenation syntax.
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