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PostgreSQL DOMAIN Drop

DROP DOMAIN removes a domain. Only the owner of a domain can remove it

Syntax:
DROP DOMAIN [ IF EXISTS ] name [, ...] [ CASCADE | RESTRICT ]
parameter
Explanation
IF EXISTS
Do not throw an error if the domain does not exist. A notice is issued in this case.
name
The name (optionally schema-qualified) of an existing domain.
CASCADE
Automatically drop objects that depend on the domain (such as table columns).
RESTRICT
Refuse to drop the domain if any objects depend on it. This is the default
 Examples:
To remove the domain postal_code:
Step 1. list out the Dmain using "\dD"
postgres=# \dD
                                                                       List of domains
 Schema |    Name     |         Type          |                 Modifier                  |                 
             Check                               
--------+-------------+-----------------------+-------------------------------------------+------------------------------------------------------------------
 public | addrtype    | character varying(90) | not null default 'N/A'::character varying | 
 public | idxtype     | integer               |                                           | CHECK (VALUE > 10 AND VALUE < 99)
 public | postal_code | text                  |                                           | CHECK (VALUE ~ '^\d{5}$'::text OR VALUE ~ '^\d{5}-\d{4}$'::text)
(3 rows)
Step 2.Now Let us Drop the Domain if you want to drop "addrtype" domain you need to specify "cascade" keyword otherwise it will throw errors here startingly i gave "drop domain addrtype" without "cascade" keyword for your understanding this will be throw error after that i gave "cascade" keyword why it throw error because other objects depend on it so use "CASCADE" to drop the dependent objects too
postgres=# drop domain addrtype;
ERROR:  cannot drop type addrtype because other objects depend on it
DETAIL:  table place column address depends on type addrtype
HINT:  Use DROP ... CASCADE to drop the dependent objects too.
Step 3.Now use drop domain with cascade option
postgres=# drop domain addrtype cascade;
NOTICE:  drop cascades to table place column address
DROP DOMAIN
Step 4.Now check domain
postgres=# \dD                          
                                               List of domains
 Schema |    Name     |  Type   | Modifier |                              Check                             
  
--------+-------------+---------+----------+------------------------------------------------------------------
 public | idxtype     | integer |          | CHECK (VALUE > 10 AND VALUE < 99)
 public | postal_code | text    |          | CHECK (VALUE ~ '^\d{5}$'::text OR VALUE ~ '^\d{5}-\d{4}$'::text)
(2 rows)


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