SQL generating values


Example

Most databases do not have a native way of generating a series of numbers for ad-hoc use; however, common table expressions can be used with recursion to emulate that type of function.

The following example generates a common table expression called Numbers with a column i which has a row for numbers 1-5:

--Give a table name `Numbers" and a column `i` to hold the numbers
WITH Numbers(i) AS (
    --Starting number/index
    SELECT 1
    --Top-level UNION ALL operator required for recursion
    UNION ALL
    --Iteration expression:
    SELECT i + 1
    --Table expression we first declared used as source for recursion
    FROM Numbers
    --Clause to define the end of the recursion
    WHERE i < 5
)
--Use the generated table expression like a regular table
SELECT i FROM Numbers;
i
1
2
3
4
5

This method can be used with any number interval, as well as other types of data.