PostgreSQL supports an impressive number of standard SQL features in an outstanding quality. Yet there remain some cases where other databases exceed PostgreSQL’s capabilities in regard to standard SQL conformance. This session presents the gaps found during an in-depth comparison of selected standard SQL features among six popular SQL databases. The selected features include, among others, window functions and common tables expressions—both of them were recently introduced to MySQL and MariaDB. PostgreSQL supports an impressive number of standard SQL features in an outstanding quality. Yet there remain some cases where other databases exceed PostgreSQL’s capabilities in regard to standard SQL conformance. This session presents the gaps found during an in-depth comparison of selected standard SQL features among six popular SQL databases. The selected features include, among others, window functions and common tables expressions—both of them were recently introduced to MySQL and MariaDB. The comparison uses a set of conformance tests I use for my website modern-sql.com. These tests are based on the SQL:2016 standard and attempt to do a rather complete test of the requirements set out in the standard. This includes the correct declared type of expressions as well as the correct SQLSTATE in case of errors (teaser: nobody seems to care about SQLSTATE). This presentation covers two aspects: (1) features not supported by PostgreSQL but by other databases; (2) features available in PostgreSQL that are less complete or conforming as in other databases.