I have a table A with three columns a b c. I want to insert values in to columns a and b based on the join of column c with another table B

I am using the following query 

```
MERGE INTO A
USING
(SELECT * FROM B) **B**
ON (B.c=A.c)
WHEN MATCHED THEN
INSERT(a,b) VALUES(local_varialble,'STRING');

```

I am getting the following error

```
PL/SQL : ORA-00905 : MISSING KEYWORD

```

Please help !! This query always seems to be tricky 

EDIT : I found out that using != in the ON condition and following it up with WHEN NOT MATCHED compiles perfectly.. but I don't know whether it yields the correct result