Michael Glaesemann wrote:
Without using UNION, (which would require writing a select statement
for each category), how would LIMIT allow him to do this for each
category in a single query?
You're right, it would need a UNION, and a SELECT per category.
So there'd be another SELECT to find all the categories beforehand.
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
