Disallowing NULLs
/*
mysql> DROP TABLE Employee;
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE Employee (
-> Name VARCHAR(50) NOT NULL,
-> Phone VARCHAR(15) NOT NULL
-> );
Query OK, 0 rows affected (0.08 sec)
mysql> Describe Employee;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| Name | varchar(50) | | | | |
| Phone | varchar(15) | | | | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.01 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 ('John Doe', NULL);
ERROR 1048 (23000): Column 'Phone' cannot be null
mysql> Select * from Employee;
+----------+----------+
| Name | Phone |
+----------+----------+
| Joe Wang | 666 2323 |
| John Doe | |
+----------+----------+
2 rows in set (0.00 sec)
*/
DROP TABLE Employee;
CREATE TABLE Employee (
Name VARCHAR(50) NOT NULL,
Phone VARCHAR(15) 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 ('John Doe', NULL);
Select * from Employee;
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