IA201 - Whether two rows whose column values are all the null value are considered unique with nulls distinct, or unique with nulls not distinct


BigQuery 2025-09-02aaDb2 (LUW) 12.1.2aaDerby 10.17.1.0H2 2.3.232MariaDB 12.0.2MySQL 9.3.0Oracle DB 23.9PostgreSQL 17SQL Server 2022SQLite 3.50.0IA201: nulls distinctIA201: nulls not distinct
  1. Doesn’t support null-able columns in unique constraints (T591)

Normative References

The implementation defined item IA201, “Whether two rows whose column values are all the null value are considered unique with nulls distinct, or unique with nulls not distinct” is defined in ISO/IEC 9075-2:2023. It first appeared in 2023. Previously, nulls distinct was the standard behavior.

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