Re: Can you help me with this query? - Mailing list pgsql-general

Hi Mike,<br /><br /> If your foreign keys are all single-attribute, you can solve the problem easily by only using the
firstelement of each key.<br /><br /> I like to use the following view to examine foreign keys:<br /><br /> CREATE VIEW
fkeyAS<br />  SELECT t.relname AS tab, c.attname AS col, ft.relname AS ftab, fc.attname AS fcol<br />  FROM
pg_constraintfk<br />   INNER JOIN pg_class t ON fk.conrelid=t.oid<br />   INNER JOIN pg_attribute c ON
fk.conkey[1]=c.attnumAND c.attrelid=t.oid<br />   INNER JOIN pg_class ft ON fk.confrelid=ft.oid<br />   INNER JOIN
pg_attributefc ON fk.confkey[1]=fc.attnum AND fc.attrelid=ft.oid<br />  WHERE fk.contype = 'f'<br /> ;<br /><br /> Note
"confkey[1]=..."in the join condition.  Of course, if the FK uses multiple columns at either end the whole thing
becomesrapidly useless.  <br /><br /> HTH<br /><br /> BJ<br /><br /><br /><a class="moz-txt-link-abbreviated"
href="mailto:mike.griffin@mygenerationsoftware.com">mike.griffin@mygenerationsoftware.com</a>wrote: <blockquote
cite="mid46038.168.215.73.114.1087316384.squirrel@168.215.73.114"type="cite"><pre wrap="">Joe, I'm sorry but I cannot
createfunctions or anything like that, it's
 
all has to be a select statement (or series of select statements). Users
pull up our product and browse all the databases and scheme's and such, if
we asked them to create functions or if we did it through calls it would
be intrusive.

I tried to flatten out the function into a nested query but couldn't quite
get it right, is it possible to embed the select statement in the function
into the main select statement?

- Mike

 </pre><blockquote type="cite"><pre wrap=""><a class="moz-txt-link-abbreviated"
href="mailto:mike.griffin@mygenerationsoftware.com">mike.griffin@mygenerationsoftware.com</a>wrote:   </pre><blockquote
type="cite"><prewrap="">The query below will return all of the foreign keys in the current
 
schema,
I get the ForeignKey name as FK_NAME and both the primary and foreign
table's name and schema, now I just need the columns involved in the
foreign key itself, there is a column called confkey in pg_constraint
and
it's an array?  It holds the column id     </pre></blockquote><pre wrap="">It is an array because foreign keys can have
morethan one participating
 
field -- how do you want that represented? Here's a way that you can get
an array of the participating field names, assuming you're using
Postgres 7.4.x:

create or replace function getattnames(oid, smallint[])
returns name[] as '  select array(select attname from pg_attribute               where attrelid = $1               and
attnum= any ($2))
 
' language sql;

SELECT cl.relname as TABLE_NAME,       cr.relname as FK_TABLE_NAME,       getattnames(ct.conrelid, ct.conkey) as
TBL_ATTS,      getattnames(ct.confrelid, ct.confkey) as FK_TBL_ATTS
 
FROM pg_constraint ct
JOIN pg_class cl ON cl.oid=conrelid
JOIN pg_namespace nl ON nl.oid=cl.relnamespace
JOIN pg_class cr ON cr.oid=confrelid
JOIN pg_namespace nr ON nr.oid=cr.relnamespace
LEFT OUTER JOIN pg_description des ON des.objoid=ct.oid
WHERE contype='f';
     table_name     |   fk_table_name    |  tbl_atts   | fk_tbl_atts
--------------------+--------------------+-------------+------------- rule_and_refint_t3 | rule_and_refint_t1 |
{id3a,id3b}| {id1a,id1b} rule_and_refint_t3 | rule_and_refint_t2 | {id3a,id3c} | {id2a,id2c} fktable            |
pktable           | {fk}        | {id} clstr_tst          | clstr_tst_s        | {b}         | {rf_a}
 
(4 rows)

HTH,

Joe

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