sql alias field

Question

in SQL, supposes I need to refer to an aliased field in the having clause but the alias has quotes, how do I do that?

select (select...) as '005'
group by ...
having '005'>0

Answer 1

I think you are missing a FROM clause, and you should use backticks instead of single quotes:

SELECT (SELECT ...) AS `005`
FROM table1
GROUP BY ...
HAVING `005` > 0

It would help if you posted your full query, as I am guessing a bit here as to what you want to do.

Answer 2

The SQL-92 standard defines using double quotes for a column alias, rather than single quotes. In most databases, unusual characters are only allowed if you use double quotes.

That said, not all databases support referring to a column alias (in the same query) in the GROUP BY or HAVING clauses. For portable queries, I don't recommend the practice of referring to a column alias in the GROUP BY or HAVING clauses. Additionally, the HAVING clause is for aggregates - the simplified example you provided should trigger an error because no aggregate function (IE: COUNT, AVG, MIN/MAX, etc) is performed on the 005 column alias.

The following works for me on MySQL 4.1:

  SELECT COUNT(*) AS "005"
    FROM TABLE t
GROUP BY ...
  HAVING `005` > 0