History
The history of temporal databases is synchronous with the history of databases itself. With the development of SQL and its attendant use in real-life applications, people realized that when they added date columns to key fields, some issues arose. The basic issue is this: if you have a primary key and some attributes in the table, and you add a date to the primary key to track historical changes, you can suddenly give out the original key over and over again. Deletes get different meaning. And so forth. In 1992, this issue was recognized but standard database theory was not yet up to resolving this issue, and neither was the then-newly-formalized SQL-92 standard.
Richard Snodgrass proposed in 1992 that temporal extensions to SQL be developed by the temporal database community. In response to this proposal, a virtual committee was formed to design extensions to the 1992 edition of the SQL standard (ANSI X3.135.-1992 and ISO/IEC 9075:1992); those extensions, known as TSQL2, were developed during 1993 by this committee meeting only via email. In late 1993,Snodgrass first presented this work to the group responsible for the American National Standard for Database Language SQL, ANSI Technical Committee X3H2 (now known as NCITS H2). The preliminary language specification appeared in the March 1994 ACM SIGMOD Record. Based on responses to that specification, changes were made to the language, and the definitive version of the TSQL2 Language Specification was published in September, 1994
An attempt was made to incorporate parts of TSQL2 into the new SQL standard SQL:1999, called SQL3. Parts of TSQL2 were included in a new substandard of SQL3, ISO/IEC 9075-7, called SQL/Temporal. The ISO project responsible for temporal support was canceled near the end of 2001. The TSQL2 approach was heavily criticized by Chris Date and Hugh Darwen. As of December 2011, ISO/IEC 9075, Database Language SQL:2011 Part 2: SQL/Foundation included clauses in table definitions to define "application-time period tables" (valid-time tables) and "system-versioned tables" (transaction-time tables). A substantive difference between the TSQL2 proposal and what was adopted in SQL:2011 is that there are no hidden columns in the SQL:2011 treatment, nor does it have a new data type for intervals; instead two date or timestamp columns can be bound together using a PERIOD FOR declaration. Another is replacement of the controversial (prefix) statement modifiers from TSQL2 with a small set of predicates.
Read more about this topic: Temporal Database
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