How to create fast database queries

Archive for July 25th, 2009

MySQL: selecting rows before and after filtered one

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From Stack Overflow:

I have a basic MySQL table, terms, comprised of an id and term field.

I want to create an alphabetically sorted dictionary index (in the literal sense), that would list ten 10 terms above the selected term, and 20 below it

An example of this could be found on Urban Dictionary where on the left column you see the current term highlighted, and a number of terms above it, and some below, all sorted alphabetically.

As we all know, MySQL doesn't support a ROW_NUMBER() or a similar function so we end up resorting to user variables and sub-selects.

I also cannot create a view with user defined variables because MySQL doesn't allow that.

MySQL indeed doesn't support ROW_NUMBER() and this function indeed can be emulated using session variables:

However, it will be an overkill in this case, since a more simple and more efficient set-based solution using LIMIT can be used instead.

Let's create a sample table and see how:

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Written by Quassnoi

July 25th, 2009 at 11:00 pm

Posted in MySQL