psql in SQL

To see which queries psql is running under the hood do

\set ECHO_HIDDEN on
\d table_name

Take queries and run yourself, for example

get table id

SELECT c.oid,
  n.nspname,
  c.relname
FROM pg_catalog.pg_class c
     LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relname OPERATOR(pg_catalog.~) '^(table_name)$' COLLATE pg_catalog.default
  AND pg_catalog.pg_table_is_visible(c.oid)
ORDER BY 2, 3;

use it list columns

SELECT a.attname,
  pg_catalog.format_type(a.atttypid, a.atttypmod),
  (SELECT pg_catalog.pg_get_expr(d.adbin, d.adrelid, true)
   FROM pg_catalog.pg_attrdef d
   WHERE d.adrelid = a.attrelid AND d.adnum = a.attnum AND a.atthasdef),
  a.attnotnull,
  (SELECT c.collname FROM pg_catalog.pg_collation c, pg_catalog.pg_type t
   WHERE c.oid = a.attcollation AND t.oid = a.atttypid AND a.attcollation <> t.typcollation) AS attcollation,
  a.attidentity,
  a.attgenerated
FROM pg_catalog.pg_attribute a
WHERE a.attrelid = '18073' AND a.attnum > 0 AND NOT a.attisdropped
ORDER BY a.attnum;

use it list indexes

SELECT c2.relname, i.indisprimary, i.indisunique, i.indisclustered, i.indisvalid, pg_catalog.pg_get_indexdef(i.indexrelid, 0, true),
  pg_catalog.pg_get_constraintdef(con.oid, true), contype, condeferrable, condeferred, i.indisreplident, c2.reltablespace
FROM pg_catalog.pg_class c, pg_catalog.pg_class c2, pg_catalog.pg_index i
  LEFT JOIN pg_catalog.pg_constraint con ON (conrelid = i.indrelid AND conindid = i.indexrelid AND contype IN ('p','u','x'))
WHERE c.oid = '18073' AND c.oid = i.indrelid AND i.indexrelid = c2.oid
ORDER BY i.indisprimary DESC, c2.relname;