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* About "Alter table... alter column.. TYPE ... "
@ 2005-04-18 20:38 Ying Lu <ying_lu@cs.concordia.ca>
0 siblings, 1 reply; 2+ messages in thread
From: Ying Lu @ 2005-04-18 20:38 UTC (permalink / raw)
To: pgsql-sql
Hello,
To alter table column from varchar(32) to date. "Alter table" command
does not seem to work:
alter table test alter column col type date ;
ERROR: column "col1" cannot be cast to type "date"
Tks,
Emi
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: About "Alter table... alter column.. TYPE ... "
@ 2005-04-18 21:09 Rod Taylor <pg@rbt.ca>
parent: Ying Lu <ying_lu@cs.concordia.ca>
0 siblings, 0 replies; 2+ messages in thread
From: Rod Taylor @ 2005-04-18 21:09 UTC (permalink / raw)
To: Ying Lu <ying_lu@cs.concordia.ca>; +Cc: pgsql-sql
> To alter table column from varchar(32) to date. "Alter table" command
> does not seem to work:
>
> alter table test alter column col type date ;
> ERROR: column "col1" cannot be cast to type "date"
Alter table will not automatically throw away information. That is, in
cases where it believes you may lose data, it will not perform it.
That said, you can coax it into doing so.
ALTER TABLE test ALTER COLUMN col TYPE date USING CAST(col AS date);
USING is an arbitrary expression capable of doing most things you can do
in an UPDATE.
--
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2005-04-18 20:38 About "Alter table... alter column.. TYPE ... " Ying Lu <ying_lu@cs.concordia.ca>
2005-04-18 21:09 ` Rod Taylor <pg@rbt.ca>
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