Carlos Aviles Carlos Aviles - 5 months ago 17
SQL Question

How to get column attributes query from table name using PostgreSQL?

I have a project and I need a query to get all attributes of the columns (Column Name, Position, Data Type, Not Null? and Comments) all this using table name.

I achieved get Column Name, Position Data Type and Not Null? with this query:

SELECT column_name, data_type, ordinal_position, is_nullable
FROM information_schema."columns"
WHERE "table_name"='TABLE-NAME'


But, I need the Comments!

Answer

Here's query against the system catalog that should fetch everything you need (with a bonus primary-key field thrown in for free).

SELECT DISTINCT
    a.attnum as num,
    a.attname as name,
    format_type(a.atttypid, a.atttypmod) as typ,
    a.attnotnull as notnull, 
    com.description as comment,
    coalesce(i.indisprimary,false) as primary_key,
    def.adsrc as default
FROM pg_attribute a 
JOIN pg_class pgc ON pgc.oid = a.attrelid
LEFT JOIN pg_index i ON 
    (pgc.oid = i.indrelid AND i.indkey[0] = a.attnum)
LEFT JOIN pg_description com on 
    (pgc.oid = com.objoid AND a.attnum = com.objsubid)
LEFT JOIN pg_attrdef def ON 
    (a.attrelid = def.adrelid AND a.attnum = def.adnum)
WHERE a.attnum > 0 AND pgc.oid = a.attrelid
AND pg_table_is_visible(pgc.oid)
AND NOT a.attisdropped
AND pgc.relname = 'TABLE_NAME'  -- Your table name here
ORDER BY a.attnum;

Which would return results like:

 num |    name     |             typ             | notnull |       comment       | primary_key 
-----+-------------+-----------------------------+---------+---------------------+-------------
   1 | id          | integer                     | t       | a primary key thing | t
   2 | ref         | text                        | f       |                     | f
   3 | created     | timestamp without time zone | t       |                     | f
   4 | modified    | timestamp without time zone | t       |                     | f
   5 | name        | text                        | t       |                     | f
  • num: The column number
  • name: The column name
  • typ: the data type
  • notnull: Is the column defined as NOT NULL
  • comment: Any COMMENT defined for the column
  • primary_key: Is the column defined as PRIMARY KEY
  • default: The command used for the default value