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) Heynitz: 035242/47212, D1: 0160/7141639 GnuPG-ID 0x3FFF606C http://wwwkeys.de.pgp.net === 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.