From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Bruno Wolff III <bruno(at)wolff(dot)to> |
Cc: | Vinay <vinay(at)mdp(dot)net>, pgsql-admin(at)postgresql(dot)org |
Subject: | Re: Newbie question |
Date: | 2003-06-27 02:47:42 |
Message-ID: | 23574.1056682062@sss.pgh.pa.us |
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Lists: | pgsql-admin |
Bruno Wolff III <bruno(at)wolff(dot)to> writes:
>> I want the column to accept the column value which is absolutely length of two.
> A char(2) will always have two characters (unless it is NULL). If you want
> to check for two nonblank characters or two letters or something like
> that use a check constraint.
> Some like:
> create table test (
> col1 char(2) constraint bad_length check (col1 ~ '^[a-zA-Z][a-zA-Z]$'
> );
The most obvious way to my mind is
check(length(rtrim(col1)) = 2)
if "length" is simply defined as "number of characters excluding
trailing blanks". If you want a more complex check then something
like Bruno's example will probably get the job done.
If you are going to apply a constraint like this then I'd counsel just
declaring the column as text --- making it char(2) simply means that
the system is applying an extra check that is redundant with your
constraint.
regards, tom lane
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