In accordance with ANSI/ISO SQL standards, SQL Anywhere supports the LEFT OUTER, RIGHT OUTER, and FULL OUTER keywords. For compatibility with Adaptive Server Enterprise prior to version 12, SQL Anywhere also supports the Transact-SQL counterparts of these keywords, *= and =*, providing the tsql_outer_joins database option is set to On. See tsql_outer_joins option [compatibility].

There are some limitations and potential problems with the Transact-SQL semantics. For a detailed discussion of Transact-SQL outer joins, see the whitepaper Semantics and Compatibility of Transact-SQL Outer Joins, which is available at  http://www.sybase.com/detail?id=1017447.

In the Transact-SQL dialect, you create outer joins by supplying a comma-separated list of tables in the FROM clause, and using the special operators *= or =* in the WHERE clause. In Adaptive Server Enterprise prior to version 12, the join condition must appear in the WHERE clause (ON was not supported).

Example

The following left outer join lists all customers and finds their order dates (if any):

SELECT GivenName, Surname, OrderDate
FROM Customers, SalesOrders
WHERE Customers.ID *= SalesOrders.CustomerID
ORDER BY OrderDate;

This statement is equivalent to the following statement, in which ANSI/ISO syntax is used:

SELECT GivenName, Surname, OrderDate
FROM Customers LEFT OUTER JOIN SalesOrders
ON Customers.ID = SalesOrders.CustomerID
ORDER BY OrderDate;