Просмотр исходного текста страницы PostgreSQL/Constraints/Default

==Add and DROP DEFAULT==



   
  <!-- start source code -->
   
    <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==



   
  <!-- start source code -->
   
    <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==



   
  <!-- start source code -->
   
    <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==



   
  <!-- start source code -->
   
    <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>