PostgreSQL/Constraints/Default
Содержание
Add and DROP DEFAULT
<source lang="sql">
postgres=# postgres=# -- Creating the books table postgres=# postgres=# CREATE TABLE books ( postgres(# id integer UNIQUE, postgres(# title text NOT NULL, postgres(# author_id integer, postgres(# subject_id integer, postgres(# CONSTRAINT books_id_pkey PRIMARY KEY (id)); NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "books_id_pkey" for table "books" CREATE TABLE postgres=# postgres=# \d books
Table "public.books" Column | Type | Modifiers
+---------+-----------
id | integer | not null title | text | not null author_id | integer | subject_id | integer |
Indexes:
"books_id_pkey" PRIMARY KEY, btree (id)
postgres=# postgres=# -- Altering column defaults postgres=# postgres=# ALTER TABLE books ALTER COLUMN id SET DEFAULT nextval("book_ids"); ERROR: relation "book_ids" does not exist postgres=# postgres=# postgres=# \d books
Table "public.books" Column | Type | Modifiers
+---------+-----------
id | integer | not null title | text | not null author_id | integer | subject_id | integer |
Indexes:
"books_id_pkey" PRIMARY KEY, btree (id)
postgres=# postgres=# ALTER TABLE books ALTER id DROP DEFAULT; ALTER TABLE postgres=# postgres=# \d books
Table "public.books" Column | Type | Modifiers
+---------+-----------
id | integer | not null title | text | not null author_id | integer | subject_id | integer |
Indexes:
"books_id_pkey" PRIMARY KEY, btree (id)
postgres=# postgres=# postgres=# drop table books; DROP TABLE postgres=#
</source>
Changing a Column"s Default Value
<source lang="sql">
postgres=# postgres=# CREATE TABLE employee ( postgres(# ID int, postgres(# name varchar(10), postgres(# salary real, postgres(# start_date date, postgres(# city varchar(10), postgres(# region char(1) postgres(# ); CREATE TABLE postgres=# postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (1, "Jason", 40420, "02/01/94", "New York", "W"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (2, "Robert",14420, "01/02/95", "Vancouver","N"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (3, "Celia", 24020, "12/03/96", "Toronto", "W"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (4, "Linda", 40620, "11/04/97", "New York", "N"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (5, "David", 80026, "10/05/98", "Vancouver","W"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (6, "James", 70060, "09/06/99", "Toronto", "N"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (7, "Alison",90620, "08/07/00", "New York", "W"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (8, "Chris", 26020, "07/08/01", "Vancouver","N"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (9, "Mary", 60020, "06/09/02", "Toronto", "W"); INSERT 0 1 postgres=# postgres=# select * from employee;
id | name | salary | start_date | city | region
+--------+--------+------------+-----------+--------
1 | Jason | 40420 | 1994-02-01 | New York | W 2 | Robert | 14420 | 1995-01-02 | Vancouver | N 3 | Celia | 24020 | 1996-12-03 | Toronto | W 4 | Linda | 40620 | 1997-11-04 | New York | N 5 | David | 80026 | 1998-10-05 | Vancouver | W 6 | James | 70060 | 1999-09-06 | Toronto | N 7 | Alison | 90620 | 2000-08-07 | New York | W 8 | Chris | 26020 | 2001-07-08 | Vancouver | N 9 | Mary | 60020 | 2002-06-09 | Toronto | W
(9 rows) postgres=# postgres=# postgres=# -- Changing a Column"s Default Value postgres=# postgres=# ALTER TABLE employee ALTER COLUMN salary SET DEFAULT 7.77; ALTER TABLE postgres=# postgres=# \d employee;
Table "public.employee" Column | Type | Modifiers
+-----------------------+--------------
id | integer | name | character varying(10) | salary | real | default 7.77 start_date | date | city | character varying(10) | region | character(1) |
postgres=# postgres=# drop table employee; DROP TABLE postgres=# postgres=#
</source>
Create table with default column value
<source lang="sql">
postgres=# postgres=# CREATE TABLE products ( postgres(# product_no integer, postgres(# name text, postgres(# price numeric DEFAULT 9.99 postgres(# ); CREATE TABLE postgres=# postgres=# drop table products; DROP TABLE postgres=# postgres=#
</source>
To remove any default value
<source lang="sql">
postgres=# postgres=# CREATE TABLE employee ( postgres(# ID int, postgres(# name varchar(10), postgres(# salary real, postgres(# start_date date, postgres(# city varchar(10), postgres(# region char(1) postgres(# ); CREATE TABLE postgres=# postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (1, "Jason", 40420, "02/01/94", "New York", "W"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (2, "Robert",14420, "01/02/95", "Vancouver","N"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (3, "Celia", 24020, "12/03/96", "Toronto", "W"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (4, "Linda", 40620, "11/04/97", "New York", "N"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (5, "David", 80026, "10/05/98", "Vancouver","W"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (6, "James", 70060, "09/06/99", "Toronto", "N"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (7, "Alison",90620, "08/07/00", "New York", "W"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (8, "Chris", 26020, "07/08/01", "Vancouver","N"); INSERT 0 1 postgres=# insert into employee (ID, name, salary, start_date, city, region) postgres-# values (9, "Mary", 60020, "06/09/02", "Toronto", "W"); INSERT 0 1 postgres=# postgres=# select * from employee;
id | name | salary | start_date | city | region
+--------+--------+------------+-----------+--------
1 | Jason | 40420 | 1994-02-01 | New York | W 2 | Robert | 14420 | 1995-01-02 | Vancouver | N 3 | Celia | 24020 | 1996-12-03 | Toronto | W 4 | Linda | 40620 | 1997-11-04 | New York | N 5 | David | 80026 | 1998-10-05 | Vancouver | W 6 | James | 70060 | 1999-09-06 | Toronto | N 7 | Alison | 90620 | 2000-08-07 | New York | W 8 | Chris | 26020 | 2001-07-08 | Vancouver | N 9 | Mary | 60020 | 2002-06-09 | Toronto | W
(9 rows) postgres=# postgres=# -- To remove any default value postgres=# postgres=# ALTER TABLE employee ALTER COLUMN salary DROP DEFAULT; ALTER TABLE postgres=# postgres=# \d employee;
Table "public.employee" Column | Type | Modifiers
+-----------------------+-----------
id | integer | name | character varying(10) | salary | real | start_date | date | city | character varying(10) | region | character(1) |
postgres=# postgres=# drop table employee; DROP TABLE postgres=# postgres=#
</source>