[Aloisius]

MS SQL Server treats NULLs as indistinct for UNIQUE constraints, SELECT DISTINCT and for UNION.

Indeed, the sqlite page the pull quote is from says as much.

[hans_castorp]

> MS SQL Server treats NULLs as indistinct for UNIQUE constraints

Postgres lets you control that behaviour when creating the constraint (or index)

[swiftcoder]

Although only in relatively recent versions. I had to hack around this in TypeOrm, because their Postgres backend hasn't exposed the option yet.