Slow distinct query in SQL Server over large dataset

Question

We\'re using SQL Server 2005 to track a fair amount of constantly incoming data (5-15 updates per second). We noticed after it has been in production for a couple months that on

Answer 1

There is an isse with the SQL Server optimizer when using the DISTINCT keyword. The solution was to force it to keep the same query plan by breaking out the distinct query separately.

So we too queries such as:

SELECT DISTINCT [typeName] FROM [types] WITH (nolock);

and break it up into the following

SELECT typeName INTO #tempTable1 FROM types WITH (NOLOCK)
SELECT DISTINCT typeName FROM #tempTable1

Another way to get around it is to use a GROUP BY, which gets a different optimization plan.