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Displaying posts with tag: FIND_IN_SET (reset)

MySQL: Another Ranking trick
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I just read SQL: Ranking without self join, in which Shlomi Noach shares a nice MySQL-specific trick based on user-defined variables to compute rankings.

Shlomi's trick reminds me somewhat of the trick I came across little over a year ago to caclulate percentiles. At that time, several people pointed …

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A fun use of SUBSTRING_INDEX and friends in MySQL
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I used to develop with MySQL, and those were the golden days. These days I don’t write queries so much. But yesterday I needed to answer this question: are there any issues in our issue-tracking system that meet the following criteria?

  • The last two or more emails are from the customer
  • These emails were separated by at least two hours (i.e. it wasn’t a single train of thought)

I could do it with all kinds of correlated subqueries and so on — but maybe I could also just do it without them, no? Can this be done with plain old JOINS and GROUP BY? I’m sure you know the answer.

Here’s …

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