What does a sign mean in an Oracle SQL WHERE clause

Question

Possible Duplicate    Oracle  What does     do in a WHERE clause        Consider the simplified SQL query below  in an Oracle database environment  although I m not sure that it s Oracle-specific    SELECT     t0 foo  t1 bar FROM    FIRST TABLE t0  SECOND TABLE t1 WHERE    t0 ID       t1 ID    What is that     notation for in the WHERE clause   I m sorry if this is an ignorant newbie question  but it s been extremely difficult to search for on Google or StackOverflow    because even when using quote marks  search engines see a     sign and seem to want to treat it as some kind of a logical directive

User · Accepted Answer

This is an Oracle-specific notation for an outer join. It means that it will include all rows from t1, and use NULLS in the t0 columns if there is no corresponding row in t0.

In standard SQL one would write:

SELECT t0.foo, t1.bar
  FROM FIRST_TABLE t0
 RIGHT OUTER JOIN SECOND_TABLE t1;

Oracle recommends not to use those joins anymore if your version supports ANSI joins (LEFT/RIGHT JOIN) :

Oracle recommends that you use the FROM clause OUTER JOIN syntax rather than the Oracle join operator. Outer join queries that use the Oracle join operator (+) are subject to the following rules and restrictions […]

[sql] What does a (+) sign mean in an Oracle SQL WHERE clause?

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