MySQL Tutorial/Table/Foreign Keys
Содержание
Add Index and primary key to a table in table creation command
mysql>
mysql> CREATE TABLE myTable
-> (
-> OrderID SMALLINT UNSIGNED NOT NULL,
-> ModelID SMALLINT UNSIGNED NOT NULL,
-> PRIMARY KEY (OrderID),
-> INDEX (ModelID)
-> );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> desc myTable;
+---------+----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+----------------------+------+-----+---------+-------+
| OrderID | smallint(5) unsigned | NO | PRI | | |
| ModelID | smallint(5) unsigned | NO | MUL | | |
+---------+----------------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql>
mysql> drop table myTable;
Query OK, 0 rows affected (0.00 sec)
Alter table to drop primary key and foreign key
mysql>
mysql>
mysql> CREATE TABLE Publishers
-> (
-> PubID SMALLINT NOT NULL DEFAULT 1
-> )
-> ENGINE=INNODB;
Query OK, 0 rows affected (0.08 sec)
mysql>
mysql>
mysql> CREATE TABLE Books
-> (
-> BookID SMALLINT NOT NULL,
-> BookName VARCHAR(40) NOT NULL,
-> PubID SMALLINT NOT NULL DEFAULT 1
-> )
-> ENGINE=INNODB;
Query OK, 0 rows affected (0.06 sec)
mysql>
mysql>
mysql> ALTER TABLE Books
-> ADD PRIMARY KEY (BookID),
-> ADD CONSTRAINT fk_1 FOREIGN KEY (PubID) REFERENCES Publishers (PubID),
-> ADD COLUMN Format ENUM("paperback", "hardcover") NOT NULL AFTER BookName;
ERROR 1005 (HY000): Can"t create table ".\test\#sql-a98_3a.frm" (errno: 150)
mysql>
mysql> desc Books;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| BookID | smallint(6) | NO | | | |
| BookName | varchar(40) | NO | | | |
| PubID | smallint(6) | NO | | 1 | |
+----------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql>
mysql> desc Publishers;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| PubID | smallint(6) | NO | | 1 | |
+-------+-------------+------+-----+---------+-------+
1 row in set (0.01 sec)
mysql>
mysql>
mysql>
mysql> ALTER TABLE Books
-> DROP PRIMARY KEY,
-> DROP FOREIGN KEY fk_1,
-> DROP COLUMN Format;
ERROR 1091 (42000): Can"t DROP "PRIMARY"; check that column/key exists
mysql>
mysql>
mysql> desc Books;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| BookID | smallint(6) | NO | | | |
| BookName | varchar(40) | NO | | | |
| PubID | smallint(6) | NO | | 1 | |
+----------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql>
mysql> desc Publishers;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| PubID | smallint(6) | NO | | 1 | |
+-------+-------------+------+-----+---------+-------+
1 row in set (0.01 sec)
mysql>
mysql> drop table Books;
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> drop table Publishers;
Query OK, 0 rows affected (0.03 sec)
FOREIGN KEY ON DELETE CASCADE ON UPDATE CASCADE
mysql>
mysql> CREATE TABLE Models
-> (
-> ModelID SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
-> Name VARCHAR(40) NOT NULL,
-> PRIMARY KEY (ModelID)
-> );
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql> CREATE TABLE Orders
-> (
-> ID SMALLINT UNSIGNED NOT NULL PRIMARY KEY,
-> ModelID SMALLINT UNSIGNED NOT NULL,
-> Description VARCHAR(40),
-> FOREIGN KEY (ModelID) REFERENCES Models (ModelID)
-> ON DELETE CASCADE ON UPDATE CASCADE
-> );
Query OK, 0 rows affected (0.05 sec)
mysql>
mysql>
mysql> desc Models;
+---------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+----------------------+------+-----+---------+----------------+
| ModelID | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| Name | varchar(40) | NO | | | |
+---------+----------------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)
mysql>
mysql> desc Orders;
+-------------+----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+----------------------+------+-----+---------+-------+
| ID | smallint(5) unsigned | NO | PRI | | |
| ModelID | smallint(5) unsigned | NO | MUL | | |
| Description | varchar(40) | YES | | NULL | |
+-------------+----------------------+------+-----+---------+-------+
3 rows in set (0.01 sec)
mysql>
mysql> drop table Orders;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> drop table Models;
Query OK, 0 rows affected (0.00 sec)
mysql>
Implement a many-to-many map
mysql>
mysql>
mysql> CREATE TABLE Books(
-> BookID SMALLINT NOT NULL PRIMARY KEY,
-> BookTitle VARCHAR(60) NOT NULL,
-> Copyright YEAR NOT NULL
-> )
-> ENGINE=INNODB;
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql>
mysql> INSERT INTO Books VALUES (12786, "Java", 1934),
-> (13331, "MySQL", 1919),
-> (14356, "PHP", 1966),
-> (15729, "PERL", 1932),
-> (16284, "Oracle", 1996),
-> (17695, "Pl/SQL", 1980),
-> (19264, "JavaScript", 1992),
-> (19354, "www.sqle.ru", 1993);
Query OK, 8 rows affected (0.05 sec)
Records: 8 Duplicates: 0 Warnings: 0
mysql>
mysql>
mysql> CREATE TABLE Authors(
-> AuthID SMALLINT NOT NULL PRIMARY KEY,
-> AuthFN VARCHAR(20),
-> AuthMN VARCHAR(20),
-> AuthLN VARCHAR(20)
-> )
-> ENGINE=INNODB;
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql>
mysql> INSERT INTO Authors VALUES (1006, "H", "S.", "T"),
-> (1007, "J", "C", "O"),
-> (1008, "B", NULL, "E"),
-> (1009, "R", "M", "R"),
-> (1010, "J", "K", "T"),
-> (1011, "J", "G.", "N"),
-> (1012, "A", NULL, "P"),
-> (1013, "A", NULL, "W"),
-> (1014, "N", NULL, "A");
Query OK, 9 rows affected (0.02 sec)
Records: 9 Duplicates: 0 Warnings: 0
mysql>
mysql>
mysql> CREATE TABLE AuthorBook(
-> AuthID SMALLINT NOT NULL,
-> BookID SMALLINT NOT NULL,
-> PRIMARY KEY (AuthID, BookID),
-> FOREIGN KEY (AuthID) REFERENCES Authors (AuthID),
-> FOREIGN KEY (BookID) REFERENCES Books (BookID)
-> )
-> ENGINE=INNODB;
Query OK, 0 rows affected (0.05 sec)
mysql>
mysql>
mysql> INSERT INTO AuthorBook VALUES (1006, 14356),
-> (1008, 15729),
-> (1009, 12786),
-> (1010, 17695),
-> (1011, 15729),
-> (1012, 19264),
-> (1012, 19354),
-> (1014, 16284);
Query OK, 8 rows affected (0.03 sec)
Records: 8 Duplicates: 0 Warnings: 0
mysql>
mysql>
mysql> select * from Authors;
+--------+--------+--------+--------+
| AuthID | AuthFN | AuthMN | AuthLN |
+--------+--------+--------+--------+
| 1006 | H | S. | T |
| 1007 | J | C | O |
| 1008 | B | NULL | E |
| 1009 | R | M | R |
| 1010 | J | K | T |
| 1011 | J | G. | N |
| 1012 | A | NULL | P |
| 1013 | A | NULL | W |
| 1014 | N | NULL | A |
+--------+--------+--------+--------+
9 rows in set (0.00 sec)
mysql> select * from Books;
+--------+----------------+-----------+
| BookID | BookTitle | Copyright |
+--------+----------------+-----------+
| 12786 | Java | 1934 |
| 13331 | MySQL | 1919 |
| 14356 | PHP | 1966 |
| 15729 | PERL | 1932 |
| 16284 | Oracle | 1996 |
| 17695 | Pl/SQL | 1980 |
| 19264 | JavaScript | 1992 |
| 19354 | www.sqle.ru | 1993 |
+--------+----------------+-----------+
8 rows in set (0.00 sec)
mysql> select * from AuthorBook;
+--------+--------+
| AuthID | BookID |
+--------+--------+
| 1009 | 12786 |
| 1006 | 14356 |
| 1008 | 15729 |
| 1011 | 15729 |
| 1014 | 16284 |
| 1010 | 17695 |
| 1012 | 19264 |
| 1012 | 19354 |
+--------+--------+
8 rows in set (0.00 sec)
mysql>
mysql> SELECT BookTitle, Copyright, AuthID
-> FROM Books AS b, AuthorBook AS ab
-> WHERE b.BookID=ab.BookID
-> ORDER BY BookTitle;
+----------------+-----------+--------+
| BookTitle | Copyright | AuthID |
+----------------+-----------+--------+
| Java | 1934 | 1009 |
| JavaScript | 1992 | 1012 |
| Oracle | 1996 | 1014 |
| PERL | 1932 | 1008 |
| PERL | 1932 | 1011 |
| PHP | 1966 | 1006 |
| Pl/SQL | 1980 | 1010 |
| www.sqle.ru | 1993 | 1012 |
+----------------+-----------+--------+
8 rows in set (0.00 sec)
mysql>
mysql> drop table AuthorBook;
Query OK, 0 rows affected (0.01 sec)
mysql> drop table Books;
Query OK, 0 rows affected (0.05 sec)
mysql> drop table Authors;
Query OK, 0 rows affected (0.06 sec)
mysql>
mysql>
One table with two foreign keys
mysql>
mysql> CREATE TABLE Books(
-> BookID SMALLINT NOT NULL PRIMARY KEY,
-> BookTitle VARCHAR(60) NOT NULL,
-> Copyright YEAR NOT NULL
-> )
-> ENGINE=INNODB;
Query OK, 0 rows affected (0.05 sec)
mysql>
mysql>
mysql> INSERT INTO Books VALUES (12786, "Java", 1934),
-> (13331, "MySQL", 1919),
-> (14356, "PHP", 1966),
-> (15729, "PERL", 1932),
-> (16284, "Oracle", 1996),
-> (17695, "Pl/SQL", 1980),
-> (19264, "JavaScript", 1992),
-> (19354, "www.sqle.ru", 1993);
Query OK, 8 rows affected (0.05 sec)
Records: 8 Duplicates: 0 Warnings: 0
mysql>
mysql>
mysql> CREATE TABLE Authors(
-> AuthID SMALLINT NOT NULL PRIMARY KEY,
-> AuthFN VARCHAR(20),
-> AuthMN VARCHAR(20),
-> AuthLN VARCHAR(20)
-> )
-> ENGINE=INNODB;
Query OK, 0 rows affected (0.05 sec)
mysql>
mysql>
mysql> INSERT INTO Authors VALUES (1006, "H", "S.", "T"),
-> (1007, "J", "C", "O"),
-> (1008, "B", NULL, "E"),
-> (1009, "R", "M", "R"),
-> (1010, "J", "K", "T"),
-> (1011, "J", "G.", "N"),
-> (1012, "A", NULL, "P"),
-> (1013, "A", NULL, "W"),
-> (1014, "N", NULL, "A");
Query OK, 9 rows affected (0.03 sec)
Records: 9 Duplicates: 0 Warnings: 0
mysql>
mysql>
mysql> CREATE TABLE AuthorBook(
-> AuthID SMALLINT NOT NULL,
-> BookID SMALLINT NOT NULL,
-> PRIMARY KEY (AuthID, BookID),
-> FOREIGN KEY (AuthID) REFERENCES Authors (AuthID),
-> FOREIGN KEY (BookID) REFERENCES Books (BookID)
-> )
-> ENGINE=INNODB;
Query OK, 0 rows affected (0.05 sec)
mysql>
mysql>
mysql> INSERT INTO AuthorBook VALUES (1006, 14356),
-> (1008, 15729),
-> (1009, 12786),
-> (1010, 17695),
-> (1011, 15729),
-> (1012, 19264),
-> (1012, 19354),
-> (1014, 16284);
Query OK, 8 rows affected (0.03 sec)
Records: 8 Duplicates: 0 Warnings: 0
mysql>
mysql>
mysql> select * from Authors;
+--------+--------+--------+--------+
| AuthID | AuthFN | AuthMN | AuthLN |
+--------+--------+--------+--------+
| 1006 | H | S. | T |
| 1007 | J | C | O |
| 1008 | B | NULL | E |
| 1009 | R | M | R |
| 1010 | J | K | T |
| 1011 | J | G. | N |
| 1012 | A | NULL | P |
| 1013 | A | NULL | W |
| 1014 | N | NULL | A |
+--------+--------+--------+--------+
9 rows in set (0.00 sec)
mysql> select * from Books;
+--------+----------------+-----------+
| BookID | BookTitle | Copyright |
+--------+----------------+-----------+
| 12786 | Java | 1934 |
| 13331 | MySQL | 1919 |
| 14356 | PHP | 1966 |
| 15729 | PERL | 1932 |
| 16284 | Oracle | 1996 |
| 17695 | Pl/SQL | 1980 |
| 19264 | JavaScript | 1992 |
| 19354 | www.sqle.ru | 1993 |
+--------+----------------+-----------+
8 rows in set (0.00 sec)
mysql> select * from AuthorBook;
+--------+--------+
| AuthID | BookID |
+--------+--------+
| 1009 | 12786 |
| 1006 | 14356 |
| 1008 | 15729 |
| 1011 | 15729 |
| 1014 | 16284 |
| 1010 | 17695 |
| 1012 | 19264 |
| 1012 | 19354 |
+--------+--------+
8 rows in set (0.00 sec)
mysql>
mysql>
mysql> SELECT BookTitle, AuthID FROM Books, AuthorBook;
+----------------+--------+
| BookTitle | AuthID |
+----------------+--------+
| Java | 1006 |
| MySQL | 1006 |
| PHP | 1006 |
| PERL | 1006 |
| Oracle | 1006 |
| Pl/SQL | 1006 |
| JavaScript | 1006 |
| www.sqle.ru | 1006 |
| Java | 1008 |
| MySQL | 1008 |
| PHP | 1008 |
| PERL | 1008 |
| Oracle | 1008 |
| Pl/SQL | 1008 |
| JavaScript | 1008 |
| www.sqle.ru | 1008 |
| Java | 1009 |
| MySQL | 1009 |
| PHP | 1009 |
| PERL | 1009 |
| Oracle | 1009 |
| Pl/SQL | 1009 |
| JavaScript | 1009 |
| www.sqle.ru | 1009 |
| Java | 1010 |
| MySQL | 1010 |
| PHP | 1010 |
| PERL | 1010 |
| Oracle | 1010 |
| Pl/SQL | 1010 |
| JavaScript | 1010 |
| www.sqle.ru | 1010 |
| Java | 1011 |
| MySQL | 1011 |
| PHP | 1011 |
| PERL | 1011 |
| Oracle | 1011 |
| Pl/SQL | 1011 |
| JavaScript | 1011 |
| www.sqle.ru | 1011 |
| Java | 1012 |
| MySQL | 1012 |
| PHP | 1012 |
| PERL | 1012 |
| Oracle | 1012 |
| Pl/SQL | 1012 |
| JavaScript | 1012 |
| www.sqle.ru | 1012 |
| Java | 1012 |
| MySQL | 1012 |
| PHP | 1012 |
| PERL | 1012 |
| Oracle | 1012 |
| Pl/SQL | 1012 |
| JavaScript | 1012 |
| www.sqle.ru | 1012 |
| Java | 1014 |
| MySQL | 1014 |
| PHP | 1014 |
| PERL | 1014 |
| Oracle | 1014 |
| Pl/SQL | 1014 |
| JavaScript | 1014 |
| www.sqle.ru | 1014 |
+----------------+--------+
64 rows in set (0.00 sec)
mysql>
mysql> drop table AuthorBook;
Query OK, 0 rows affected (0.03 sec)
mysql> drop table Books;
Query OK, 0 rows affected (0.06 sec)
mysql> drop table Authors;
Query OK, 0 rows affected (0.05 sec)
Using AUTO_INCREMENT
The AUTO_INCREMENT attribute can be used to generate a unique identity for new rows:
mysql>
mysql> CREATE TABLE employee (
-> id MEDIUMINT NOT NULL AUTO_INCREMENT,
-> name CHAR(30) NOT NULL,
-> PRIMARY KEY (id)
-> );
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql> desc employee;
+-------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+----------------+
| id | mediumint(9) | NO | PRI | NULL | auto_increment |
| name | char(30) | NO | | | |
+-------+--------------+------+-----+---------+----------------+
2 rows in set (0.02 sec)
mysql>
mysql> INSERT INTO employee (name) VALUES ("A"),
-> ("B"),
-> ("C"),
-> ("D"),
-> ("E"),
-> ("F");
Query OK, 6 rows affected (0.00 sec)
Records: 6 Duplicates: 0 Warnings: 0
mysql>
mysql> SELECT * FROM employee;
+----+------+
| id | name |
+----+------+
| 1 | A |
| 2 | B |
| 3 | C |
| 4 | D |
| 5 | E |
| 6 | F |
+----+------+
6 rows in set (0.00 sec)
mysql>
mysql> drop table employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
Using Foreign Keys
In MySQL, InnoDB tables support checking of foreign key constraints.
For non-InnoDB tables, REFERENCES tbl_name(col_name) clause has no actual effect.
It serves only as a comment to the column.
mysql> CREATE TABLE person (
-> id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
-> name CHAR(60) NOT NULL,
-> PRIMARY KEY (id)
-> );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> CREATE TABLE shirt (
-> id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
-> owner SMALLINT UNSIGNED NOT NULL REFERENCES person(id),
-> PRIMARY KEY (id)
-> );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> desc person;
+-------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| name | char(60) | NO | | | |
+-------+----------------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)
mysql> desc shirt;
+-------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------------------+------+-----+---------+----------------+
| id | smallint(5) unsigned | NO | PRI | NULL | auto_increment |
| owner | smallint(5) unsigned | NO | | | |
+-------+----------------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)
mysql>
mysql> drop table shirt;
Query OK, 0 rows affected (0.00 sec)
mysql> drop table person;
Query OK, 0 rows affected (0.02 sec)
mysql>
mysql>