в 13:45, 26 мая 2010

2010-05-26T13:45:56Z

Admin: 1 версия

2010-05-26T10:14:32Z

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==Adding a constraint to an existing table: add foreign key to table==



<source lang="sql">

postgres=# CREATE TABLE "books" (
postgres(# "id" integer NOT NULL,
postgres(# "title" text NOT NULL,
postgres(# "author_id" integer,
postgres(# "subject_id" integer,
postgres(# Constraint "books_id_pkey" Primary Key ("id")
postgres(# );
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "books_id_pkey" for table "books"
CREATE TABLE
postgres=# -- Adding a constraint to an existing table
postgres=#
postgres=# ALTER TABLE books ADD CONSTRAINT legal_subjects
postgres-# FOREIGN KEY (subject_id)
postgres-# REFERENCES subjects (id);
ALTER TABLE
postgres=#
postgres=# drop table books;
DROP TABLE
postgres=#

</source>

==Adding constraints (FOREIGN KEY) to a table==



<source lang="sql">

postgres=#
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));
ERROR: relation "books" already exists
postgres=#
postgres=# create table editions (
postgres(# edition_id integer,
postgres(# book_id integer
postgres(# );
CREATE TABLE
postgres=#
postgres=#
postgres=# -- Adding constraints to a table
postgres=#
postgres=# ALTER TABLE editions
postgres-# ADD CONSTRAINT foreign_book
postgres-# FOREIGN KEY (book_id) REFERENCES books (id);
ALTER TABLE
postgres=#
postgres=# drop table books cascade;
NOTICE: drop cascades to constraint foreign_book on table editions
DROP TABLE
postgres=#
postgres=# drop table editions cascade;
DROP TABLE
postgres=#

</source>

==ALTER TABLE employee ADD FOREIGN KEY (group_id) REFERENCES product_groups==



<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=# ALTER TABLE employee ADD FOREIGN KEY (group_id) REFERENCES product_groups;
ERROR: relation "product_groups" does not exist
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>

==Create FOREIGN KEY==



<source lang="sql">

postgres=#
postgres=# CREATE TABLE "books" (
postgres(# "id" integer NOT NULL,
postgres(# "title" text NOT NULL,
postgres(# "author_id" integer,
postgres(# "subject_id" integer,
postgres(# Constraint "books_id_pkey" Primary Key ("id")
postgres(# );
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "books_id_pkey" for table "books"
CREATE TABLE
postgres=#
postgres=# CREATE TABLE editions
postgres-# (isbn text,
postgres(# book_id integer,
postgres(# edition integer,
postgres(# publisher_id integer,
postgres(# publication date,
postgres(# type char,
postgres(# CONSTRAINT pkey PRIMARY KEY (isbn),
postgres(# CONSTRAINT integrity CHECK (book_id IS NOT NULL
postgres(# AND edition IS NOT NULL),
postgres(# CONSTRAINT book_exists FOREIGN KEY (book_id)
postgres(# REFERENCES books (id)
postgres(# ON DELETE CASCADE
postgres(# ON UPDATE CASCADE);
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "pkey" for table "editions"
CREATE TABLE
postgres=#
postgres=# drop table books cascade;
NOTICE: drop cascades to constraint book_exists on table editions
DROP TABLE
postgres=# drop table editions cascade;
DROP TABLE
postgres=#

</source>

==Define foreign key for a table==



<source lang="sql">

postgres=#
postgres=# -- Foreign Keys
postgres=#
postgres=# CREATE TABLE products (
postgres(# product_no integer PRIMARY KEY,
postgres(# name text,
postgres(# price numeric
postgres(# );
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "products_pkey" for table "products"
CREATE TABLE
postgres=#
postgres=# CREATE TABLE orders (
postgres(# order_id integer PRIMARY KEY,
postgres(# product_no integer REFERENCES products (product_no),
postgres(# quantity integer
postgres(# );
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "orders_pkey" for table "orders"
CREATE TABLE
postgres=#
postgres=# drop table products cascade;
NOTICE: drop cascades to constraint orders_product_no_fkey on table orders
DROP TABLE
postgres=# drop table orders cascade;
DROP TABLE
postgres=#
postgres=#

</source>

==Reference two two columns as foreign key column==



<source lang="sql">

postgres=#
postgres=#
postgres=# CREATE TABLE products (
postgres(# product_no integer PRIMARY KEY,
postgres(# name text,
postgres(# price numeric
postgres(# );
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "products_pkey" for table "products"
CREATE TABLE
postgres=#
postgres=# CREATE TABLE orders (
postgres(# order_id integer PRIMARY KEY,
postgres(# shipping_address text
postgres(# );
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "orders_pkey" for table "orders"
CREATE TABLE
postgres=#
postgres=# CREATE TABLE order_items (
postgres(# product_no integer REFERENCES products,
postgres(# order_id integer REFERENCES orders,
postgres(# quantity integer,
postgres(# PRIMARY KEY (product_no, order_id)
postgres(# );
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "order_items_pkey" for table "order_items"
CREATE TABLE
postgres=#
postgres=#
postgres=# drop table products cascade;
NOTICE: drop cascades to constraint order_items_product_no_fkey on table order_items
DROP TABLE
postgres=# drop table orders cascade;
NOTICE: drop cascades to constraint order_items_order_id_fkey on table order_items
DROP TABLE
postgres=# drop table order_items cascade;
DROP TABLE
postgres=#
postgres=#

</source>

==Using foreign keys==



<source lang="sql">

postgres=#
postgres=# -- Foreign Keys
postgres=#
postgres=# CREATE TABLE cities (
postgres(# city varchar(80) primary key,
postgres(# id int
postgres(# );
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "cities_pkey" for table "cities"
CREATE TABLE
postgres=#
postgres=# CREATE TABLE weather (
postgres(# city varchar(80) references cities(city),
postgres(# temp_lo int,
postgres(# temp_hi int,
postgres(# prcp real,
postgres(# date date
postgres(# );
CREATE TABLE
postgres=#
postgres=# insert into cities values ("Berkeley", 0);
INSERT 0 1
postgres=#
postgres=# INSERT INTO weather VALUES ("Berkeley", 45, 53, 0.0, "1994-11-28");
INSERT 0 1
postgres=#
postgres=# drop table weather;
DROP TABLE
postgres=# drop table cities;
DROP TABLE
postgres=#
postgres=#

</source>

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PostgreSQL/Constraints/FOREIGN KEY - История изменений

в 13:45, 26 мая 2010

Admin: 1 версия