Question

I have a sql query with 50 parameters, such as this one.

DECLARE   @p0 int, @p1 int, @p2 int, (text omitted), @p49 int  SELECT   @p0=111227, @p1=146599, @p2=98917, (text omitted), @p49=125319  -- SELECT   [t0].[CustomerID], [t0].[Amount],   [t0].[OrderID], [t0].[InvoiceNumber] FROM [dbo].[Orders] AS [t0] WHERE ([t0].[CustomerID]) IN   (@p0, @p1, @p2, (text omitted), @p49) 

The estimated execution plan shows that the database will collect these parameters, order them, and then read the index Orders.CustomerID from the smallest parameter to the largest, then do a bookmark lookup for the rest of the record.

The problem is that there the smallest and largest parameter could be quite far apart and this will lead to reading possibly the entire index.

Since this is being done in a loop from the client side (50 params sent each time, for 1000 iterations), this is a bad situation. How can I formulate the query/client side code to get my data without repetitive index scanning while keeping the number of round trips down?

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I thought about ordering the 50k parameters such that smaller readings of the index would occur. There is a wierd mitigating circumstance that prevents this – I can’t use this solution. To model this circumstance, just assume that I only have 50 id’s available at any time and can’t control their relative position in the global list.

Answer 1

Insert the parameters into a temporary table, then join it with your table:

DECLARE @params AS TABLE(param INT);  INSERT INTO    @params VALUES  (@p1) ... INSERT INTO    @params VALUES  (@p49)  SELECT   [t0].[CustomerID], [t0].[Amount],   [t0].[OrderID], [t0].[InvoiceNumber] FROM @params, [dbo].[Orders] AS [t0] WHERE ([t0].[CustomerID]) = @params.param 

This will most probably use NESTED LOOPS with a INDEX SEEK over CustomerID on each loop.