SQL For .NET Programmers

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November 2013
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Posts Tagged ‘cursor’

SQL CURSOR Performance – SQL For Programmers

Last week I showed how to use the SQL CURSOR to loop through records in a database.  In that article I mentioned that you want to avoid using the CURSOR if you can because it has performance problems.

The article was posted on DZone where a self-proclaimed SQL guru picked it up and left a comment basically stating an alternate way of looping through records that would do the same thing but didn’t require the CURSOR.  What he suggested was the common practice of doing something like this:

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SQL CURSOR – SQL For Programmers

ka_vol1_143 One of the things it took me a while to figure out was how to get a stored procedure to loop through data in a table and pull out specific data I needed.

There are actually two parts to this question.  First, you should always try to find some other way of doing whatever it is you think you need to do by processing one row at a time.  SQL is a “Set-Based” language and as such it expects you to work with the whole set.  That’s what it was designed to do best and that’s why it has functions such as MAX, MIN, SUM, AVG, etc.  Many of these functions in combination with a good WHERE clause will get you the information you need.

However, there are times when you’ll need to process the information one record at a time, and this is what the CURSOR was created for.

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