Conformity
After some years while our grammar and parser matured we reached not only full conformity with the server parser, but could even add language features that aren’t released yet. Our grammar is as close to the server parser as one can be and is the most complete grammar you can get for free (as part of the MySQL Workbench package, which ships the grammar not only in the source zip, but also in the binary package, because it is needed for code completion, or download it MySQL.g). Once in a while (also before big releases) we scan all changes in the server’s sql_yacc.y file and incorporate them, to stay up to date.
Additionally, we have a large set of unit tests that check proper behavior of the generated parser. Some of them (e.g. the sql mode and operator precedence tests) were taken from the MySQL server tests. We have a set of ~1000 queries of all types, to cover most of the language and a special set of commands that stress the use of identifiers (as documented for MySQL) as well as huge table definitions with hundreds of columns and indices etc.