Interview Q&A / PostgreSQL
PostgreSQL interview questions
Indexes, EXPLAIN, transactions and isolation, JSONB and the Postgres specifics backend interviews probe.
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- Can a UNIQUE column in PostgreSQL contain more than one NULL?
Yes by default, because NULL is unknown and two unknowns are not considered equal. From PostgreSQL 15 you can add NULLS NOT DISTINCT to make NULLs count as duplicates.
IntermediateQuick answer1 min read