Semantics and Compatiblity of Transact-SQL Outer Joins

Transact-SQL outer joins are specified using the special comparison operators '* ='and '= *'. Using one (or more) of these operators in a query specifies an outer join between two tables in the From clause, though the semantics of such queries can be unclear. This is because TSQL outer join semantics were never formally defined, and in older releases of Adaptive Server Enterprise and Adaptive Server Anywhere the results of TSQL outer join queries could depend upon the access plan chosen by the optimizer. This Anywhere Solutions' Technical White Paper describes the semantics of TSQL outer joins in detail, and in particular outlines the differences in support for TSQL outer joins between ASE and ASA. Because of these differences, Anywhere Solutions recommends that customers use ANSI outer join syntax, rather than Transact-SQL outer join syntax, in their applications.

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