To keep it simple, let me keep it this way: Considering two table A and B and internal table ITAB: Inner Join: It requires an entry with KEY of A in B, to be extracted to internal table. Outer Join: Irrespective of whether an entry exists or not in B it still extracts data from A. Eg:
Table: A
--------
Fld1 Fld2
------------
X 100
Y 200
Z 300
Table: B
--------
Fld1 Fld3
------------
X abc
X def
Z pqr " No entry for Key Y in table B so it is not extracted
ITAB fields: FLD1, FLD2, FLD3
Inner Join:
-----------
FLD1 FLD2 FLD3
--------------------
X 100 abc
X 100 def
Z 300 pqr
Outer Join:
-----------
FLD1 FLD2 FLD3
--------------------
X 100 abc
X 100 def
Y 200 " No entry for Key Y in table B so FLD3 is blank
Z 300 pqr
