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Re: Converting char to varchar automatically

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On 10/6/2014 5:29 AM, Andrus wrote:
Database contains about 300 tables.
Most of them contain columns of char(n) type.
How to convert all those columns to varchar automatically ?
Is it possible to run some update commands in system tables for this ?
Or is it possible to create pgsql script which creates dynamically alter
table alter column commands and PERFORMs them ?
Any tables have primary keys with char(n) columns and foreign keys on
them. Foreign keys are deferrable and initially  immediate.
Will foreign keys allow to perform such alter table alter column commands ?
Or is there better way.
Andrus.

I'd use a little perl.

Or if your editor has macros, you could use that.

change:
create table bob (
	id char(50),
..
)

to

alter table bob alter id type varchar(50);

You might be able to query them out if you wanted:

select table_name, column_name, character_maximum_length
from information_schema.columns
where data_type = 'character'

Then use that to generate the alter table commands. Hum... this might also work:

select 'alter table ' || table_name || ' alter ' || column_name .... etc

but that might try changing system tables which would be bad.

-Andy



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