Re: [SQL] Mail about typecast

Vikrant Rathore ha scritto:

> Dear friends,
>
> I want to run a query :
>
> vikrant=> select date_part('epoch','12 hours'::timespan)::float4;
> It returns a error message
> ERROR: function dtof(float8) does not exist
>
> But i want to use typecast since the result of this query will be used
> to update a field of type float4.
>
> I have checked the pg_proc system table it has a function dtof with
> float8 as argument i have checked the list of functions also and
> 'dtof(float8)' is shown in that list also.
> can anyone solve this problem. I can solve the problem by using a c
> program but i want to know when the function dtof(float8) is there in
> pg_proc table then why it is not doing a typecasting.
> Thanks in advance for your kind suggestion.
>
> Thanks & regards,
> Vikrant.

Which version of PostgreSQL are you using?
This works for me. (v6.5)

hygea=> \df dtof
result|function|arguments|description
------+--------+---------+------------------------
float4|dtof |float8 |convert float8 to float4
(1 row)

hygea=> select date_part('epoch','12 hours'::timespan)::float4;
float4
------
43200
(1 row)

hygea=> select date_part('epoch','12 hours'::timespan);
date_part
---------
43200
(1 row)

______________________________________________________________
PostgreSQL 6.5.0 on i586-pc-linux-gnu, compiled by gcc 2.7.2.3
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Jose'