I've been searching for half an hour and can't find any resources stating what level of the SQL ANSI standard is supported on various database engines.
It looks like some level of support is provided by most engines, but I'd like to know exactly what level is officially supported.
I'm primarily interested in MySQL, PostgreSQL, SQL Server, and Oracle.
EDIT: PostgreSQL has a great page on compliance, exactly what I was looking for regarding the other engines: http://www.postgresql.org/docs/current/interactive/features.html
The question of "which level of the standard" is too simple.
There are portions of the standard that are implemented by no engine at all, e.g. CREATE ASSERTION.
For that reason, it might be better to speak of "percentage of standard features supported" for each individual engine. But the vendors will be very reluctant to publish such measurements themselves.
The PostgreSQL manual has for all SQL statements a compatibility section.
According to the HSQLDB manual, it is the most standards compliant RDBMS.
- Almost all syntactic features of SQL-92 up to Advanced Level are supported
- SQL:2008 core and many optional features of this standard
Firebird 3 sql standard conformance page
来源：https://stackoverflow.com/questions/3602617/database-engines-and-ansi-sql-compliance