#1054 - Unknown column 'start' in 'where clause'
SELECT SUBSTRING_INDEX(`age_in_day`, '-', 1) as start, SUBSTRING_INDEX(`age_in_day`, '-', -1) FROM `volume_limit` where start <= 32 and end >= 32;
You can only use column aliases in GROUP BY, ORDER BY, or HAVING clauses.
Standard SQL doesn't allow you to refer to a column alias in a WHERE clause. This restriction is imposed because when the WHERE code is executed, the column value may not yet be determined.
Copied from MySQL documentation
As pointed in the comments, using HAVING instead may do the work. Make sure to give a read at this WHERE vs HAVING though.