Does a database column that has numbers need to be indexed?

Question

Suppose Bob has earned 107 points, Mary 105 points and John also 105 points. These numbers could change and are not unique. Now I want to query and check the order, who is on top and who is on the bottom. Does that column that holds points need to be indexed ?

Answer 1

It depends on the database system used and the size (number of rows) of the table.

If the table is small enough and you're using MSSQL for example, a table scan will be used (the entire table will be read into memory) and an index will be relatively useless.

Generally speaking, yes - the field should be indexed if that is the column you'll be using to select or sort data.

Answer 2

As a very general rule, I consider indexing columns that appear in the WHERE or ORDER BY clauses of commonly executed queries.