Mysql Alter Remove Column
Mysql Alter Remove Column is used to redefine the table and remove the column from existing table.
Understand with Example
The Tutorial illustrate an example from 'Mysql Alter Remove Column'. To understand this example we create a table 'employees'. The create table create a table employees and empid as primary key.
Query to create table:-
CREATE TABLE employees (
->Empid int(10),
->Empname varchar(60),
->city varchar(30),
->date date
->PRIMARY KEY(Empid)
->);
|
Query to insert data into Table named employees:
Once your table is created, the insert into add the records to the table'employees'.
mysql>insert into employees values(01,'Girish','2008-12-22','Nainital'); Query OK, 1 row affected (0.02 sec) mysql>insert into employee1 values(02,'Komal','2008-12-23','Meerut'); Query OK, 1 row affected (0.02 sec) |
Query to view data of Table named employees:
mysql> select * from employees; |
Output:-
+-------+---------+------------+----------+ | empid | empname | date | city | +-------+---------+------------+----------+ | 1 | Girish | 2008-12-22 | Nainital | | 2 | Komal | 2008-12-23 | Meerut | +-------+---------+------------+----------+ 2 rows in set (0.00 sec) |
Query to remove column:
The Query alter redefine the table definition and drop column is used to remove column 'city' from table 'employees'.
mysql> alter table employees
-> drop column city;
Query OK, 2 rows affected (0.11 sec)
Records: 2 Duplicates: 0 Warnings: 0
|
Output:
Now we use select query to return the new records from table employees.
mysql> select * from employees; +-------+---------+------------+ | empid | empname | date | +-------+---------+------------+ | 1 | Girish | 2008-12-22 | | 2 | Komal | 2008-12-23 | +-------+---------+------------+ 2 rows in set (0.00 sec) |