(+) function in PLSQL

Question

I'm now dealing with PLSQL developer, which is my very first time. And I find this kind of query

select * from tableA, tableB
where tableA.field1 = tableB.field1(+)

I'm wondering the function of the (+) in the query. Could you guys be so kind to explain it ?

Answer 1

where tableA.field1 = tableB.field1(+)

This is the old syntax for an outer join, adopted by Oracle, and made redundant when ANSI actually standardised the SQL language. Oracle themselves now suggest you use outer join in preference to this old syntax (from the link below):

Oracle recommends that you use the FROM clause OUTER JOIN syntax rather than the Oracle join operator.

See this entry in the Oracle docs for more detail.