Current SQL databases are designed to one of two main standards, SQL-92 and SQL:1999.
SQL-86 was the first SQL standard.
The 1992 standard, SQL-92, was the last pure SQL standard. Up until recently, MySQL aimed for compliance with SQL-92. MySQL now aims for SQL:1999.
SQL:1999 is the standard that PostgreSQL, Oracle, and a lot of other big databases followed for some years. SQL-99 introduced triggers and other things that are programming language ideas and not really part of your request. They are ways of making other things happen automatically when you make a query and may change the results you see in your queries.
SQL:2003 introduces XML and automatic sequence ids, an idea promoted by MySQL many years before SQL:2003.
SQL:2006 attempts to make XML usable in relational databases to stop people switching to specialised XML databases.
SQL:2008 adds some minor changes