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Assigning a varaiable without returning results
Posted by: Sean Nolan
Date: April 01, 2005 10:32AM

I want to check that I'm doing this the best way. I have a batch of SQL code, where I need to calculate an aggregate in SELECT and then use that value in a second SELECT. I am using MySql 4.0 so unfortunately I cannot use a subquery (which is how I'd like to do this :-)).

So I run the first SELECT and assign the aggregate to a variable something like this:
SELECT @AveragePrice := AVG(price) FROM Products;

Then I run the second SELECT, something like this:
SELECT * FROM Products WHERE price > @AveragePrice;

That works just fine, but I now get two result sets returned to the client, and I have to ignore the first one and use the second one.

I have found a workaround, in that I now use a CREATE TEMPORARY TABLE ... SELECT to run the first SELECT, it assigns the variable correctly, and then I run the second SELECT and I just get one result set on the client. It just seems like a heavy-handed way to do it. Is there a better way to assign the aggregate value to the variable without returning a result set from the first SELECT?

Thanks
Sean

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