Editing Select (SQL) (section)

=== ROW_NUMBER() window function ===
<code>ROW_NUMBER() OVER</code> may be used for a ''simple table'' on the returned rows, e.g. to return no more than ten rows:

<syntaxhighlight lang="sql" highlight="3">
SELECT * FROM
( SELECT
    ROW_NUMBER() OVER (ORDER BY sort_key ASC) AS row_number,
    columns
  FROM tablename
) AS foo
WHERE row_number <= 10

</syntaxhighlight>

ROW_NUMBER can be [[Nondeterministic algorithm|non-deterministic]]: if ''sort_key'' is not unique, each time you run the query it is possible to get different row numbers assigned to any rows where ''sort_key'' is the same. When ''sort_key'' is unique, each row will always get a unique row number.