Обсуждение: Changing datatype of a column

<br /><p><font face="Arial" size="2">              Hi,</font><p><font face="Arial" size="2">              I would like
toKnow if there any way (and what is the command for that)  to convert a column datatype</font><br /><font face="Arial"
size="2">             from int4 to numeric(11)  of an existing table that have data in it?</font><br /><font
face="Arial"size="2">              </font><br /><font face="Arial" size="2">         </font><br /><font face="Arial"
size="2">            Thanks,</font><br /><font face="Arial" size="2">             Ilan</font><p><font face="Arial"
size="2"> </font><br /><b><font color="#000000" face="Century
Gothic">_________________________________________</font></b><br/><b><font color="#000000" face="Century Gothic">ILAN
FAIT</font></b><br/><font color="#000000" face="Century Gothic" size="2">Tel: 972-9-9519133  Ex.247    iWeb
Technologies</font><br/><font color="#000000" face="Century Gothic" size="2">Fax: 972-9-9519134                91
MedinatHa'Yehudim St.</font><br /><font color="#000000" face="Century Gothic"
size="2">                                                    Herzliya 46120 IL</font><br /><font color="#000000"
face="CenturyGothic" size="2"><a href="mailto:ilan@iweb.com">mailto:ilan@iweb.com</a>    www.iweb.com</font><br /> 

Ilan Fait writes:

>               I would like to Know if there any way (and what is the command
> for that)  to convert a column datatype
>               from int4 to numeric(11)  of an existing table that have data
> in it?

No, you have to recreate the table.

-- 
Peter Eisentraut   peter_e@gmx.net   http://funkturm.homeip.net/~peter

There is no way to do this directly, but it is a
pretty simple task to do this using SELECT INTO.

Here is a trivial example of how to do this.

First of all let's say you have a table that looks
like this with some values in it:

CREATE TABLE foo (   num    int
);

processdata=> select * from foo;num 
-----  1  2  3
(3 rows)


A simple query using SELECT INTO would give you the
table that you need.

processdata=> select num::numeric(11) as num into bar
from foo;

Here's the results.

processdata=> \d bar            Table "bar"Attribute |     Type      | Modifier 
-----------+---------------+----------num       | numeric(11,0) | 

processdata=> select * from bar;num 
-----  1  2  3
(3 rows)

You can then drop the original table and use alter
table to change the name of the new table.  You can
also add constraints and whatever else you need.

Hope this is helpful,
Jason
--- Ilan Fait <ilan@iweb.com> wrote:
> 
>               Hi,
> 
>               I would like to Know if there any way
> (and what is the command
> for that)  to convert a column datatype
>               from int4 to numeric(11)  of an
> existing table that have data
> in it?
>               
>          
>              Thanks,
>              Ilan
> 
>   
> _________________________________________
> ILAN FAIT
> Tel: 972-9-9519133  Ex.247    iWeb Technologies
> Fax: 972-9-9519134                91 Medinat
> Ha'Yehudim St.
>                                                     
> Herzliya 46120 IL
> mailto:ilan@iweb.com    www.iweb.com
> 
> 
> 


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