hello

does anyone know what is returned when you do a where column without
further parameters?

SELECT * FROM TABLE WHERE COLUMN;

for integer columns it seems to return non-zero columns, but for other
types of columns the results seemed unpredictable.

----- Original Message -----
From: "Olav Mørkrid" <olav.morkrid@gmail.com>
To: <mysql@lists.mysql.com>
Sent: Friday, August 24, 2007 1:07 AM
Subject: where column


> hello
>
> does anyone know what is returned when you do a where column without
> further parameters?
>
> SELECT * FROM TABLE WHERE COLUMN;
>
> for integer columns it seems to return non-zero columns, but for other
> types of columns the results seemed unpredictable.
>
In my opinion, the statement should not execute at all since it isn't
syntactically correct. In the dialects of SQL I have used - and I've been
using SQL for a lot of years - simply saying "WHERE hiredate" (or whatever
column name you want) is an incomplete statement since the column name must
be followed by some kind of operator, such as =, <, >, LIKE, or whatever.

Despite that, I am not up-to-date on MySQL and they may support an extension
that lets you write SQL like that; in that case, the MySQL manual for your
version should make it clear what happens if you write that.

But I still think it should not execute at all. The WHERE clause is a filter
to prevent rows that don't satisfy the condition from appearing in your
result set; "WHERE columnname" is not a complete condition in my opinion so
it simply should execute.

--
Rhino

Olav Mørkrid wrote:
> hello
>
> does anyone know what is returned when you do a where column without
> further parameters?
>
> SELECT * FROM TABLE WHERE COLUMN;
>
> for integer columns it seems to return non-zero columns, but for other
> types of columns the results seemed unpredictable.
>
>
The value of the column will be converted to a TRUE or FALSE value (1 or
0). If the column would evaluate in a numerical setting to a value of 0,
the statement would read "WHERE FALSE" and not show that row. Can you
provide an example of a resultset that does not make sense to you?

Its no different than providing an actual equation to provide the true
or false condition

SELECT... FROM ... WHERE 0 will always return no data as the WHERE
condition will never be true.

--
Shawn Green, Support Engineer
MySQL Inc., USA, www.mysql.com
Office: Blountville, TN
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