default: nulls not distinct

BigQueryDb2 (LUW)MariaDBMySQLOracle DBPostgreSQLSQL ServerSQLite200520072009201120132015201720192021⊘ 3.5.7 - 3.39.0✓ 2008R2+⊘ 8.3 - 14⚠ 11gR1 - 21cb⊘ 5.0 - 8.0.30⊘ 5.1 - 10.9.2
  1. Doesn’t support null-able columns in unique constraints (T591)
  2. If some but not all constraint columns are null