On Mon, Dec 8, 2025 at 9:40 PM Igor Korot <[email protected]> wrote:
> Hi, ALL, > Consider the following scenario: > > CREATE TABLE test(a INT, b VARCHAR(256), c INT, d VARCHAR(256), /* > more fields follows*/); > CREATE UNIQUE INDEX test_x( b, c, d ); > > Now I try to do: > > INSERT INTO test VALUES( 0, 'abc', 12345, (SELECT foo FROM bar), > /*more data follow*/); > > My problem is: > > The SELECT can either return data or NULL. > Everything is good when the data is returned, but the insert fails > when the NULL is returned, because the field "d" is a part of UNIQUE > INDEX. > > However,, I'd like to still insert the record and I'd like to do something > like: > > INSERT INTO test VALUES( 0, 'abc', 12345, IF( (SELECT foo FROM bar) == > NULL, "postgres", <select_result>), /*more data follow*/); > > What would be the best way to achieve this? > https://www.postgresql.org/docs/15/sql-createindex.html section on NULLS DISTINCT says "Specifies whether for a unique index, null values should be considered distinct (not equal). *The default* is that they are *distinct*, so that a *unique index could contain multiple null values in a column*." That seems to mean multiple rows can have NULL in column "d". -- Death to <Redacted>, and butter sauce. Don't boil me, I'm still alive. <Redacted> lobster!
