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by magicalhippo 1752 days ago
Heh, perhaps it's more accurate to say I've abused recursive queries.

One instance was to turn a column containing comma separated values into rows[1], so I could join on them. Wasn't for a query that needed performance of course.

[1]: https://news.ycombinator.com/item?id=28020321
2 comments
alexanderskates 1751 days ago
I had this same issue in Redshift and ended up populating a table with values 1 to the maximum number of commas found (e.g. using max(regexp_count(...)) or something), then cross joining on the table with the csv column and calling split_part on the corresponding column and index (with the index coming from the numbers table). The cross join ensures that you index every value of the csv column.
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fifilura 1751 days ago
What I think you'd do here (in modern implementations of SQL at least) is to split the values into an array using some convenient split function and self join on that array to pivot the arrays into rows.
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magicalhippo 1751 days ago
> some convenient split function

If only the DB we're using had one of those :)

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