Re: Obtain boolean value of expression in PLPGSQL

On Tuesday 04 November 2003 10:06, Max Speransky wrote:
> Hello
>
> My task is to validate expression and get value of it in boolean variable.
> I try to do following:

>         Ret := 3 || Op || $1;
>         RETURN Ret;

> bill=# select get_value(3);
> WARNING:  Error occurred while executing PL/pgSQL function get_value
> WARNING:  line 6 at assignment
> ERROR:  Bad boolean external representation '3=3'

The problem is that your expression is being evaluated as a string. In the
absence of an eval() function, you probably should do something like:

my_stmt := ''SELECT '' || 3 || Op || $1;
EXECUTE my_stmt;
FOR EACH ...

So - build a simple query, execute it and read the result. Should do what you
want.

--
  Richard Huxton
  Archonet Ltd