I have seen a few posts, dating back as far 2007 covering the topic Mandt in index.
There is even a monster note 825653, but is too concerned with the CBO on oracle.
This is not a DB specific question. Im looking for the general, approach to indexes.
I see strong evidence for including MANDT in indexes. That also makes sense to me since it is included in the SQL each time.
What I havent found documented is why put MANDT as the first field in a index and not as the last.
Especially when the index is for a specific field in the table. Ie only 2 fields in the index.
When there a several fields in an index and they may not always be present in SQL statement,
then puting the MANDT up front makes some sense.
But for Simple single Use field index
I would have defined the index as
1) FIELD_X
2) MANDT
for use with
select * from table_Y where field_x = 'SOME_VALUE'.
why create the index as follows ?
1) MANDT
2) FIELD_X