SQL-92

SQL-92 was the third revision of the SQL database query language. Unlike SQL-89, it was a major revision of the standard. Aside from a few minor incompatibilities, the SQL-89 standard is forward-compatible with SQL-92.

The standard specification itself grew about five times compared to SQL-89. Much of it was due to more precise specifications of existing features; the increase due to new features was only by a factor of 1.5–2. Many of the new features had already been implemented by vendors before the new standard was adopted.^[1] However, most of the new features were added to the "intermediate" and "full" tiers of the specification, meaning that conformance with SQL-92 entry level was scarcely any more demanding than conformance with SQL-89.

Later revisions of the standard include SQL:1999 (SQL3), SQL:2003, SQL:2008, SQL:2011, SQL:2016 and SQL:2023.

Significant new features include:^[2]

• New data types defined: DATE, TIME, TIMESTAMP, INTERVAL, BIT string, VARCHAR strings, and NATIONAL CHARACTER strings.
• Support for additional character sets beyond the base requirement for representing SQL statements.
• New scalar operations such as string concatenation and substring extraction, date and time mathematics, and conditional statements.
• New set operations such as UNION JOIN, NATURAL JOIN, set differences, and set intersections.
• Conditional expressions with CASE. For an example, see Case (SQL).
• Support for alterations of schema definitions via ALTER and DROP.
• Bindings for C, Ada, and MUMPS.
• New features for user privileges.
• New integrity-checking functionality such as within a CHECK constraint.
• A new information schema—read-only views about database metadata like what tables it contains, etc. For example, SELECT * FROM INFORMATION_SCHEMA.TABLES;.
• Dynamic execution of queries (as opposed to prepared).
• Better support for remote database access.
• Temporary tables; CREATE TEMP TABLE etc.
• Transaction isolation levels.
• New operations for changing data types on the fly via CAST (expr AS type).
• Scrolled cursors.
• Compatibility flagging for backwards and forwards compatibility with other SQL standards.

Two significant extensions were published after standard (but before the next major iteration.)

• SQL/CLI (Call Level Interface) in 1995
• SQL/PSM (stored procedures) in 1996

• The SQL-92 standard