Oracle: What does `(+)` do in a WHERE clause?
- by Jonathan Lonowski
Found the following in an Oracle-based application that we're migrating (generalized):
SELECT
Table1.Category1,
Table1.Category2,
count(*) as Total,
count(Tab2.Stat) AS Stat
FROM Table1, Table2
WHERE (Table1.PrimaryKey = Table2.ForeignKey(+))
GROUP BY Table1.Category1, Table1.Category2
What does (+) do in a WHERE clause? I've never seen it used like that before.