Sorting By Count(*)

July 20, 2010

Sorting By Count(*)

By Bryan Young

The other day, I was working on a fairly database-centric project, when I came across a problem I had never come across before. It seemed like such a simple task that I could not fathom why I could not write the query to get what I wanted. What I needed to do was to choose only the entries in a table which appeared a certain number of times.

My first instinct told me to do something like this.

SELECT COUNT(*), name FROM tableA GROUP BY name WHERE COUNT(*) > 10;

What do you mean "Invalid use of group function"? So I start investigating, and I find out that the count function cannot be used in the WHERE section of a query. This is because SQL will process the WHERE clause before the SELECT clause in order to know just what it is searching for.

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