Altering Database Tables: Add More Columns : Alter Table « Table Index « SQL / MySQL

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SQL / MySQL » Table Index » Alter Table 
Altering Database Tables: Add More Columns

/*
mysql> CREATE TABLE Employee (
    ->    Name    VARCHAR(50) PRIMARY KEY NOT NULL,
    ->    PhoneNo VARCHAR(15) DEFAULT 'Unknown Phone',
    ->    Age     INT CHECK (Age BETWEEN 20 and 30));
Query OK, 0 rows affected (0.12 sec)

mysql> Describe Employee;
+---------+-------------+------+-----+---------------+-------+
| Field   | Type        | Null | Key | Default       | Extra |
+---------+-------------+------+-----+---------------+-------+
| Name    | varchar(50) |      | PRI |               |       |
| PhoneNo | varchar(15) | YES  |     | Unknown Phone |       |
| Age     | int(11)     | YES  |     | NULL          |       |
+---------+-------------+------+-----+---------------+-------+
3 rows in set (0.00 sec)


mysql> Select * from Employee;
+----------+---------------+------+
| Name     | PhoneNo       | Age  |
+----------+---------------+------+
| John Doe | Unknown Phone |   31 |
+----------+---------------+------+
1 row in set (0.00 sec)

mysql> ALTER TABLE Employee ADD (EMail VARCHAR(25), ICQ VARCHAR(15));
Query OK, 1 row affected (0.08 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> Describe Employee;
+---------+-------------+------+-----+---------------+-------+
| Field   | Type        | Null | Key | Default       | Extra |
+---------+-------------+------+-----+---------------+-------+
| Name    | varchar(50) |      | PRI |               |       |
| PhoneNo | varchar(15) | YES  |     | Unknown Phone |       |
| Age     | int(11)     | YES  |     | NULL          |       |
| EMail   | varchar(25) | YES  |     | NULL          |       |
| ICQ     | varchar(15) | YES  |     | NULL          |       |
+---------+-------------+------+-----+---------------+-------+
5 rows in set (0.00 sec)

mysql> Select * from Employee;
+----------+---------------+------+-------+------+
| Name     | PhoneNo       | Age  | EMail | ICQ  |
+----------+---------------+------+-------+------+
| John Doe | Unknown Phone |   31 | NULL  | NULL |
+----------+---------------+------+-------+------+
1 row in set (0.01 sec)


*/
Drop TABLE Employee;
       
CREATE TABLE Employee (
   Name    VARCHAR(50PRIMARY KEY NOT NULL, 
   PhoneNo VARCHAR(15DEFAULT 'Unknown Phone',
   Age     INT CHECK (Age BETWEEN 20 and 30));

Describe Employee;

INSERT INTO Employee (Name, Phone, AgeVALUES ('Joe Wang', '666 2323', 26);
INSERT INTO Employee (Name, AgeVALUES ('John Doe', 31);

Select * from Employee;
  
ALTER TABLE Employee ADD (EMail VARCHAR(25), ICQ VARCHAR(15));

Describe Employee;

Select * from Employee;

           
       
Related examples in the same category
1. Altering Database Tables: Add a Column
2. Altering Database Tables: Drop a Column
3. Altering Database Tables: Drop Unique Constraint and Add Primary Key
4. Alter table: add unique
5. Alter table: drop primary and foreign key
6. Alter table: add primary key, foreign key and add column
7. Altering and Dropping Tables
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