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Re: Finding primary keys

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Matlack, Brad" <matlackb(at)ogden(dot)disa(dot)mil>
Cc: "'pgsql-sql(at)postgresql(dot)org'" <pgsql-sql(at)postgresql(dot)org>
Subject: Re: Finding primary keys
Date: 2000-04-10 23:35:12
Message-ID: 26622.955409712@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-sql
"Matlack, Brad" <matlackb(at)ogden(dot)disa(dot)mil> writes:
> I'm trying to determine which fields in a table are primary keys, using a
> select statement.  

This was just discussed in connection with the ODBC driver.  The best
solution I saw was

select ta.attname, ia.attnum
from pg_attribute ta, pg_attribute ia, pg_class c, pg_index i
where c.relname = 'foo_pkey'
    AND c.oid = i.indexrelid
    AND ia.attrelid = i.indexrelid
    AND ta.attrelid = i.indrelid
    AND ta.attnum = i.indkey[ia.attnum-1]
ORDER BY ia.attnum;

where 'foo' is the table you are interested in.

You could also do just

select attname, attnum from pg_attribute a, pg_class c
where c.relname = 'foo_pkey'
    AND attrelid = c.oid
    AND attnum > 0
ORDER BY attnum;

but this'll not track renaming of columns via ALTER TABLE RENAME COLUMN,
since what it's showing you is actually the names of the columns in the
index relation, and ALTER doesn't bother to change those.

			regards, tom lane

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