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

Hacker News new | past | comments | ask | show | jobs | submit

login

SigmundA on Feb 3, 2020 | parent | context | favorite | on: Null Values in SQL Queries

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

utborin on Feb 4, 2020 [–]

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.

Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact