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A comment on Null Values in SQL Queries. Parent comment

Re:Null Values in SQL Queries by danaliv on Monday February 03, 2020 @10:55PM (#22232236)
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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