RE: postgresql rookie needs help with system catalog

If you run psql with the –E flag at start then it will echo the queries used to generate all of the \ commands.

SELECT n.nspname as "Schema",
c.relname as "Name",
CASE c.relkind WHEN 'r' THEN 'table' WHEN 'v' THEN 'view' WHEN 'm' THEN 'materialized view' WHEN 'i' THEN 'index' WHEN 'S' THEN 'sequence' WHEN 's' THEN 'special' WHEN 'f' THEN
'foreign table' WHEN 'p' THEN 'table' WHEN 'I' THEN 'index' END as "Type",
pg_catalog.pg_get_userbyid(c.relowner) as "Owner"
FROM pg_catalog.pg_class c
LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relkind IN ('r','p','v','m','S','f','')
AND n.nspname <> 'pg_catalog'
AND n.nspname <> 'information_schema'
AND n.nspname !~ '^pg_toast'
AND pg_catalog.pg_table_is_visible(c.oid)
ORDER BY 1,2;

From: barry kimelman [mailto:perlmaster56(at)gmail(dot)com]
Sent: Wednesday, January 22, 2020 8:52 AM
To: pgsql-novice(at)lists(dot)postgresql(dot)org
Subject: postgresql rookie needs help with system catalog

I am trying to come up with a query of the system catalog tables to give me the same info as the psql command "\d tablename"

so far I have come up with the following query
1 SELECT
2 a.attname as "Column",
3 pg_catalog.format_type(a.atttypid, a.atttypmod) as "Datatype"
4 FROM
5 pg_catalog.pg_attribute a
6 WHERE
7 a.attnum > 0
8 AND NOT a.attisdropped
9 AND a.attrelid = (
10 SELECT c.oid
11 FROM pg_catalog.pg_class c
12 LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
13 WHERE c.relname = 'laptop'
14 AND pg_catalog.pg_table_is_visible(c.oid)
15 );

which yields the following result

Column | Datatype
---------------+------------------------
id | integer
name | character varying(250)
price | double precision
purchase_date | date
(4 rows)

But how do I get the Collation and Nullable and Default values displayed by the "psql \d" command ?

Thanks.
--

Barrry Kimelman
Winnipeg, Manitoba, Canada
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