Setting a Primary Key 1
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/*
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 Yin', '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 Yin', NULL);
ERROR 1048 (23000): Column 'Phone' cannot be null
mysql> Select * from Employee;
+----------+---------------+
| Name | Phone |
+----------+---------------+
| Joe Yin | 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 Yin', '666 2323');
INSERT INTO Employee (Name) VALUES ('John Doe');
INSERT INTO Employee (Name, Phone) VALUES ('Joe Yin', NULL);
Select * from Employee;
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