Обсуждение: Cast to integer

Hello!

Anyone could explain to me, why cast(3.33 to int) works (from float, I
suppose)  but cast('3.33' to int) (from text) does not? And what if I
create a cast for that: is it possibly dangerous?

Regards,

Robert.

On 10/5/05 9:08 AM, "Robert Osowiecki" <robson@cavern.pl> wrote:

> Hello!
>
> Anyone could explain to me, why cast(3.33 to int) works (from float, I
> suppose)  but cast('3.33' to int) (from text) does not? And what if I
> create a cast for that: is it possibly dangerous?

How about:

sdavis=# select (('3.33')::float)::int;
 int4
------
    3
(1 row)

Sean

am  05.10.2005, um 15:08:33 +0200 mailte Robert Osowiecki folgendes:
> Hello!
>
> Anyone could explain to me, why cast(3.33 to int) works (from float, I
> suppose)  but cast('3.33' to int) (from text) does not? And what if I
> create a cast for that: is it possibly dangerous?

test=# select '3.33'::float::int;
 int4
------
    3
(1 row)



Regards, Andreas
--
Andreas Kretschmer    (Kontakt: siehe Header)
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 ===    Schollglas Unternehmensgruppe    ===

Robert Osowiecki <robson@cavern.pl> writes:
> Anyone could explain to me, why cast(3.33 to int) works (from float, I
> suppose)  but cast('3.33' to int) (from text) does not?

The latter is not really a cast; it's an invocation of the int
datatype's input function.

            regards, tom lane

A. Kretschmer wrote:

>am  05.10.2005, um 15:08:33 +0200 mailte Robert Osowiecki folgendes:
>
>
>>Hello!
>>
>>Anyone could explain to me, why cast(3.33 to int) works (from float, I
>>suppose)  but cast('3.33' to int) (from text) does not? And what if I
>>create a cast for that: is it possibly dangerous?
>>
>>
>
>test=# select '3.33'::float::int;
> int4
>------
>    3
>(1 row)
>
>
>
Let me explain better. I encountered this problem when I tried to write
general unit-calculation (from kilograms to punds, for example) function
operating on any arithmetic datatype: with float and numeric it went all
ok, but failed with integer on "return $result" with error "invalid
input syntax for integer". My function internally operated on numeric
type. I wrote a wrap-around for integer, because I've been afraid, that
changing "text to integer" cast (or input function, whatever it is)
could damage something important.

R.