Indexes

711094

Hi all,

I think about if it does make sense to create an index on a column which only allows 2 different values. Here is my statement:

SELECT DISTINCT netz_nr
FROM adressen
WHERE ebene = nsp

In the column "ebene" of the table "adressen" are only the entries "nsp" or "msp", so does it makes sense with an index???

Thanks in advance! :-)

Colt

Toon Koppelaars

It depends...
If you always seek for 'nsp', and that value is present on only a few rows (and the table has many rows), then it might help you.
On the other hand of both values (nsp , and the other one) both appear on 50% each of the rows, it will not help you.