Comment

Syntax

COMMENT ON
{
  TABLE <table_name> |
  COLUMN <table_name.column_name> |
  FOREIGN TABLE <foreign_table_name>
}
IS '<text>';

Parameters

Add comments when creating a table

Wrap COMMENT ON statements in the same transaction as CREATE TABLE to add comments in a single operation.

BEGIN;
CREATE TABLE public."user" (
  "id"   text NOT NULL,
  "name" text NOT NULL
);
COMMENT ON TABLE  public."user"     IS 'user property table';
COMMENT ON COLUMN public."user".id  IS 'ID card number';
COMMENT ON COLUMN public."user".name IS 'name';
COMMIT;

Add or update comments after table creation

Run COMMENT ON statements directly against any existing table, column, or foreign table.

-- Add a comment to an internal table.
COMMENT ON TABLE table_name IS 'my comments on table table_name.';

-- Add a comment to a column.
COMMENT ON COLUMN table_name.col1 IS 'This my first col1';

-- Add a comment to a foreign table.
COMMENT ON FOREIGN TABLE foreign_table IS 'comments on my foreign table';

Query comments

To verify that comments were applied, query pg_catalog.pg_attribute. The following statement returns the column names, data types, nullable flags, and descriptions for a given table:

SELECT a.attname                                              AS "Column",
       pg_catalog.format_type(a.atttypid, a.atttypmod)       AS "Type",
       a.attnotnull                                           AS "Nullable",
       pg_catalog.col_description(a.attrelid, a.attnum)      AS "Description"
FROM   pg_catalog.pg_attribute a
WHERE  a.attnum > 0
  AND  NOT a.attisdropped
  AND  a.attrelid = '<schema.tablename>'::regclass::oid
ORDER  BY a.attnum;

Replace <schema.tablename> with the actual schema-qualified table name, for example public.user.

What's next

For other DDL statements supported by Hologres, see:

• CREATE TABLE

• CREATE TABLE AS

• CREATE TABLE LIKE

• ALTER TABLE

• DROP TABLE