A cool SQL thing I just learned

So let’s say you want to quickly populate a table with data. Until now, I’ve always done something like:

[loop from 1 to 1000]
INSERT INTO TABLE (columnA, columnB, columnC)
VALUES (columnA, columnB, columnC)

This happens a lot when I’m updating cross-table relationships, for, say, group-membership. However, I’ve learned I can do this:

INSERT INTO TABLE (columnA, columnB, columnC)
(SELECT columnA, columnB, columnC FROM TABLE_SOURCE WHERE ...)

Where, the ‘…’ is the criteria to select from the source table. I’ve no idea if this is a best practice or not, but it sure is fast! It changed an insert of 1700 rows from being about 2100 MS to being 21MS.

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