Mysql Alter Table Syntax
Mysql Alter Table is used to redefine the existing table.
| ALTER TABLE tbl_name ADD [COLUMN] col_name column_definition |
Understand with Example
The Tutorial illustrate an example from 'Mysql Alter Table'. To grasp this example we create a table 'employees'. The create table statement is used to create a table 'employees' with different fieldname and datatype respectively. The table have a Primary Key column 'empid'.
Query to create table:
CREATE TABLE employees (
->Empid int(10),
->Empname varchar(60),
->date date
->PRIMARY KEY(Empid)
->);
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Query to insert data into Table named employees:
The Query insert into add the records or rows into table 'employees'.
mysql>insert into employees values(01,'Girish','2008-12-22'); Query OK, 1 row affected (0.02 sec) mysql>insert into employee1 values(02,'Komal','2008-12-23'); Query OK, 1 row affected (0.02 sec) |
Query to view data of Table named employees:
To view the detail of table 'employees' we use select query that returns the detail of table 'employees'.
mysql> select * from employees; |
Output:-
+-------+---------+------------+ | Empid | Empname | date | +-------+---------+------------+ | 1 | Girish | 2008-12-22 | | 2 | Komal | 2008-12-23 | +-------+---------+------------+ 2 rows in set (0.00 sec) |
Query to alter Table named employees by adding column named city:
The Query Alter is used to modify the table 'employees' and add keywords is used to add the column name 'city' to the existing table.
mysql> alter table employees
-> add column city varchar(30);
Query OK, 2 rows affected (0.13 sec)
Records: 2 Duplicates: 0 Warnings: 0
|
Output:-
mysql> select * from employees; +-------+---------+------------+------+ | Empid | Empname | date | city | +-------+---------+------------+------+ | 1 | Girish | 2008-12-22 | NULL | | 2 | Komal | 2008-12-23 | NULL | +-------+---------+------------+------+ 2 rows in set (0.02 sec) |