ANSI Sql query to force return 0 records

Question

I'm looking for an ANSI-SQL method to do a Select query without returning any record, but fill a TDataSet's Fields structure.

The method I found is by adding a "where 1=0" in any query, for example:

Select Id, name, province
from customers
where 1=0

This is a fairly trivial example, it turns a little more complicated when I have to work with queries entered by the user, then parse them, remove the where clause if it already has one, and replace by "1=0".

If the last clause in the user-entered query is the where clause, then there's no problem at all, but what about more complicated queries like this:

select
  c.lastname,
  sum(cs.amount)
from customersales cs
join customers c on c.idcustomer=cs.idcustomer
/* where 1=0 */
group by c.idcustomer, c.lastname

By using the "where 1=0" method, the only way to insert it in the previous example is by having a rather powerful SQL parser (remember the user can enter complex queries, including Subqueries, and all that), who can understand where to include this string.

Does anyone knows a better way to do this? I cannot use "limit 1" because it must be in an ANSI way.

Answer 1

What about adding your own SELECT around the user's SELECT?

SELECT * FROM (
select
  c.lastname,
  sum(cs.amount)
from customersales cs
join customers c on c.idcustomer=cs.idcustomer
/* where 1=0 */
group by c.idcustomer, c.lastname
) x
WHERE 0=1

EDIT: ORDER BY would not work with that solution, but since you get no rows, you could try to remove that from the query when necessary.