в 13:46, 26 мая 2010

2010-05-26T13:46:00Z

Admin: 1 версия

2010-05-26T10:17:22Z

1 версия

Новая страница

==Define and use primary key==



<source lang="sql">
/*
mysql> Drop table Attributes;
mysql> CREATE TABLE Attributes
-> (
-> ID SMALLINT NOT NULL PRIMARY KEY,
-> Settings TINYINT UNSIGNED NOT NULL
-> );
Query OK, 0 rows affected (0.06 sec)
mysql> INSERT INTO Attributes VALUES (101, 58),
-> (102, 73),
-> (103, 45);
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> select * from Attributes;
+-----+----------+
| ID | Settings |
+-----+----------+
| 101 | 58 |
| 102 | 73 |
| 103 | 45 |
+-----+----------+
3 rows in set (0.00 sec)
*/
Drop table Attributes;
CREATE TABLE Attributes
(
ID SMALLINT NOT NULL PRIMARY KEY,
Settings TINYINT UNSIGNED NOT NULL
);

INSERT INTO Attributes VALUES (101, 58),
(102, 73),
(103, 45);
select * from Attributes;

</source>

==Setting a Primary Key 1==



<source lang="sql">
/*
mysql> Drop TABLE Employee;
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE Employee (
-> Name VARCHAR(50) NOT NULL,
-> Phone VARCHAR(15) DEFAULT "Unknown Phone" NOT NULL,
-> CONSTRAINT MyPrimaryKey PRIMARY KEY (Name));
Query OK, 0 rows affected (0.07 sec)
mysql> Describe Employee;
+-------+-------------+------+-----+---------------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------------+-------+
| Name | varchar(50) | | PRI | | |
| Phone | varchar(15) | | | Unknown Phone | |
+-------+-------------+------+-----+---------------+-------+
2 rows in set (0.01 sec)
mysql> INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", "666 2323");
Query OK, 1 row affected (0.02 sec)
mysql> INSERT INTO Employee (Name) VALUES ("John Doe");
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", NULL);
ERROR 1048 (23000): Column "Phone" cannot be null
mysql> Select * from Employee;
+----------+---------------+
| Name | Phone |
+----------+---------------+
| Joe Wang | 666 2323 |
| John Doe | Unknown Phone |
+----------+---------------+
2 rows in set (0.00 sec)
*/
Drop TABLE Employee;

CREATE TABLE Employee (
Name VARCHAR(50) NOT NULL,
Phone VARCHAR(15) DEFAULT "Unknown Phone" NOT NULL,
CONSTRAINT MyPrimaryKey PRIMARY KEY (Name));
Describe Employee;
INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", "666 2323");
INSERT INTO Employee (Name) VALUES ("John Doe");
INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", NULL);
Select * from Employee;

</source>

==Setting a Primary Key 2==



<source lang="sql">
/*
mysql> Drop TABLE Employee;
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE Employee (
-> Name VARCHAR(50) NOT NULL,
-> Phone VARCHAR(15) DEFAULT "Unknown Phone" NOT NULL,
-> PRIMARY KEY (Name));
Query OK, 0 rows affected (0.06 sec)
mysql> Describe Employee;
+-------+-------------+------+-----+---------------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------------+-------+
| Name | varchar(50) | | PRI | | |
| Phone | varchar(15) | | | Unknown Phone | |
+-------+-------------+------+-----+---------------+-------+
2 rows in set (0.00 sec)
mysql> INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", "666 2323");
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO Employee (Name) VALUES ("John Doe");
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", NULL);
ERROR 1048 (23000): Column "Phone" cannot be null
mysql> Select * from Employee;
+----------+---------------+
| Name | Phone |
+----------+---------------+
| Joe Wang | 666 2323 |
| John Doe | Unknown Phone |
+----------+---------------+
2 rows in set (0.00 sec)

*/
Drop TABLE Employee;
CREATE TABLE Employee (
Name VARCHAR(50) NOT NULL,
Phone VARCHAR(15) DEFAULT "Unknown Phone" NOT NULL,
PRIMARY KEY (Name));
Describe Employee;
INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", "666 2323");
INSERT INTO Employee (Name) VALUES ("John Doe");
INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", NULL);
Select * from Employee;

</source>

==Setting a Primary Key 3==



<source lang="sql">
/*
mysql> Drop TABLE Employee;
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE Employee (
-> Name VARCHAR(50) PRIMARY KEY NOT NULL,
-> PhoneNo VARCHAR(15) DEFAULT "Unknown Phone" NOT NULL);
Query OK, 0 rows affected (0.07 sec)
mysql> Describe Employee;
+---------+-------------+------+-----+---------------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------------+-------+
| Name | varchar(50) | | PRI | | |
| PhoneNo | varchar(15) | | | Unknown Phone | |
+---------+-------------+------+-----+---------------+-------+
2 rows in set (0.00 sec)
mysql> INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", "666 2323");
ERROR 1054 (42S22): Unknown column "Phone" in "field list"
mysql> INSERT INTO Employee (Name) VALUES ("John Doe");
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", NULL);
ERROR 1054 (42S22): Unknown column "Phone" in "field list"
mysql> Select * from Employee;
+----------+---------------+
| Name | PhoneNo |
+----------+---------------+
| John Doe | Unknown Phone |
+----------+---------------+
1 row in set (0.00 sec)

**/
Drop TABLE Employee;
CREATE TABLE Employee (
Name VARCHAR(50) PRIMARY KEY NOT NULL,
PhoneNo VARCHAR(15) DEFAULT "Unknown Phone" NOT NULL);

Describe Employee;
INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", "666 2323");
INSERT INTO Employee (Name) VALUES ("John Doe");
INSERT INTO Employee (Name, Phone) VALUES ("Joe Wang", NULL);
Select * from Employee;

</source>

← Предыдущая	Версия 13:46, 26 мая 2010
(нет различий)

SQL/MySQL/Key/Primary Key - История изменений

в 13:46, 26 мая 2010

Admin: 1 версия