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0 pointstrts6y ago0 comments

where coalesce(a, '') = coalesce(b, '')

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2 comments · 1 top-level

SigmundA6y ago· 1 in thread

Normally can't use an index as every value has to be coalesced before comparison.

You can index the results of functions (or other expressions) in at least some databases. PostgreSQL can do this, for example.

  CREATE INDEX idx ON tbl (coalesce(col, ''))

Combining this with UNIQUE can make for some neat tricks.

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