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SQL-92

SQL-92
First publishedNovember 1992
DomainSQL

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.

New features

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.

Extensions

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

References

  1. ^ Jim Melton; Alan R. Simon (1993). Understanding The New SQL: A Complete Guide. Morgan Kaufmann. pp. 11–12. ISBN 978-1-55860-245-8.
  2. ^ C. J. Date with Hugh Darwen: A Guide to the SQL standard : a users guide to the standard database language SQL, 4th ed., Addison Wesley, USA 1997, ISBN 978-0-201-96426-4
Quelle: https://en.wikipedia.org/wiki/SQL-92