Question

When I try this query:

SELECT DATE_ADD(upg_date, INTERVAL 30 DAY) AS 'upgrade_date'
WHERE id=12345

it returns me the record with the correct value, but when I add a condition like this:

SELECT DATE_ADD(upg_date, INTERVAL 30 DAY) AS 'upgrade_date'
WHERE id=12345
AND 'upgrade_date' < NOW()

it returns an empty result set. But value of the upgrade_date is lower than current date.

What’s wrong?

Answer 1

You cannot use the alias in the where clause. It should be the original column name.

SELECT DATE_ADD(upg_date, INTERVAL 30 DAY) AS upgrade_date
WHERE id=12345 AND 
      upg_date < NOW()

From the MySQL Manual:

It is not allowable to refer to a column alias in a WHERE clause, because the column value might not yet be determined when the WHERE clause is executed.