How to create fast database queries

Archive for September 22nd, 2009

Finding sets within a time frame

Comments enabled. I *really* need your comment

From Stack Overflow:

I've got a set of data that contains users, their awards and the time they are granted.

When a user earns an award, the award and user is logged along with a date.

What I'd like is a query that finds a set of 3 achievements that were earned within 5 minutes of each other by the same user.

Any thoughts on how to accomplish this?

I'll go a step further and try to build a general solution to find sets of N values within a given time frame.

We should return all rows that are parts of all 5-minute time frames containing at least N values. These timeframes can overlap.

We should build such a timeframe for each record, make sure that there are at least N values in this timeframe, and if yes, return these values (applying DISTINCT to get rid of the duplicates).

Let's create a sample table and build a query to do this:

Read the rest of this entry »

Written by Quassnoi

September 22nd, 2009 at 11:00 pm

Posted in SQL Server