SQL-92was the third revision of theSQLdatabasequery 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.
| First published | November 1992 |
|---|---|
| Domain | SQL |
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 withSQL-89.
Later revisions of the standard includeSQL:1999(SQL3),SQL:2003,SQL:2008,SQL:2011,SQL:2016andSQL:2023.
New features
editSignificant new features include:[2]
- New data types defined:
DATE,TIME,TIMESTAMP,INTERVAL,BITstring,VARCHARstrings, andNATIONAL CHARACTERstrings. - Support for additionalcharacter setsbeyond the base requirement for representing SQL statements.
- New scalar operations such as string concatenation andsubstringextraction, date and time mathematics, and conditional statements.
- New set operations such as
UNION,UNION ALL,CROSS JOIN,and formalizedJOINtypes (INNER JOIN,LEFT JOIN,RIGHT JOIN,FULL OUTER JOIN). - Conditional expressions with
CASE.For an example, seeCase (SQL). - Support for alterations ofschema definitionsvia
ALTERandDROP. - Bindings forC,Ada,andMUMPS.
- New features for user privileges.
- New integrity-checking functionality such as within a
CHECKconstraint. - A newinformation 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 TABLEetc. - Transactionisolation 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.
Extensions
editTwo 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
References
edit- ^Jim Melton; Alan R. Simon (1993).Understanding The New SQL: A Complete Guide.Morgan Kaufmann. pp.11–12.ISBN978-1-55860-245-8.
- ^C. J. DatewithHugh Darwen:A Guide to the SQL standard: a users guide to the standard database language SQL, 4th ed.,Addison Wesley, USA 1997,ISBN978-0-201-96426-4