PostgreSQL “DESCRIBE TABLE”



  • 3 Answer(s)

    The psql  command-line tool is:

    \d+ tablename
    
    Answered on December 24, 2018.
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    The PostgreSQL way \d ‘something’ or \dt ‘table’ or \ds ‘sequence’ :

    select column_name, data_type, character_maximum_length
    from INFORMATION_SCHEMA.COLUMNS where table_name = '<name of table>';
    

    It is supported  to db engines.

    Answered on December 24, 2018.
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    Alternately using psql need to obtain it from query  the catalog schema:

    SELECT
      f.attnum AS number,
      f.attname AS name,
      f.attnum,
      f.attnotnull AS notnull,
      pg_catalog.format_type(f.atttypid,f.atttypmod) AS type,
      CASE
        WHEN p.contype = 'p' THEN 't'
         ELSE 'f'
      END AS primarykey,
      CASE
        WHEN p.contype = 'u' THEN 't'
        ELSE 'f'
      END AS uniquekey,
      CASE
        WHEN p.contype = 'f' THEN g.relname
      END AS foreignkey,
      CASE
        WHEN p.contype = 'f' THEN p.confkey
      END AS foreignkey_fieldnum,
      CASE
        WHEN p.contype = 'f' THEN g.relname
      END AS foreignkey,
      CASE
        WHEN p.contype = 'f' THEN p.conkey
      END AS foreignkey_connnum,
      CASE
        WHEN f.atthasdef = 't' THEN d.adsrc
      END AS default
     FROM pg_attribute f
      JOIN pg_class c ON c.oid = f.attrelid
      JOIN pg_type t ON t.oid = f.atttypid
      LEFT JOIN pg_attrdef d ON d.adrelid = c.oid AND d.adnum = f.attnum
      LEFT JOIN pg_namespace n ON n.oid = c.relnamespace
      LEFT JOIN pg_constraint p ON p.conrelid = c.oid AND f.attnum = ANY (p.conkey)
      LEFT JOIN pg_class AS g ON p.confrelid = g.oid
    WHERE c.relkind = 'r'::char
    AND n.nspname = '%s' -- Replace with Schema name
    AND c.relname = '%s' -- Replace with table name
    AND f.attnum > 0 ORDER BY number
    ;
    

    It is the power and flexibility of the PostgreSQL system inventory and  to pg_catalog mastery . To change out the %s’s in the query. The first one is Schema and the second is the table name.

    Answered on December 24, 2018.
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