how to add a column after a particular column in mysql table

1. To add a new colmn to the existing table the ALTER command is used. Syntax:
               alter table < table name > add < column name > ;
    Example:
          To add a column called ldate to the main_tab table with a datatype of date, use the following SQL statement:
               mysql> alter table main_tab add ldate date;
            This statement will add the ldate  column to the end of the table.
2. To insert the new column after a specific column, such as name, use this statement:
   ALTER TABLE contacts ADD email VARCHAR(60) AFTER name;

mysql> alter table main_tab add ldate date after doj;
Query OK, 11 rows affected (0.12 sec)
Records: 11  Duplicates: 0  Warnings: 0

mysql> desc main_tab;
+----------+-------------+------+-----+---------+----------------+
| Field    | Type        | Null | Key | Default | Extra          |
+----------+-------------+------+-----+---------+----------------+
| acc_no   | int(5)      | NO   | PRI | NULL    | auto_increment |
| name     | varchar(20) | YES  |     | NULL    |                |
| gender   | varchar(6)  | YES  |     | NULL    |                |
| password | varchar(10) | YES  |     | NULL    |                |
| doj      | date        | YES  |     | NULL    |                |
| ldate    | date        | YES  |     | NULL    |                |
| amount   | float(10,2) | YES  |     | NULL    |                |
+----------+-------------+------+-----+---------+----------------+
7 rows in set (0.00 sec)
 
   
3. If you want the new column to be first, use this statement:
   ALTER TABLE contacts ADD email VARCHAR(60) FIRST;
   
   
4. 
   //To drop a particular column in mysql table
   
   mysql> desc main_tab;
   +----------+-------------+------+-----+---------+----------------+
   | Field    | Type        | Null | Key | Default | Extra          |
   +----------+-------------+------+-----+---------+----------------+
   | acc_no   | int(5)      | NO   | PRI | NULL    | auto_increment |
   | name     | varchar(20) | YES  |     | NULL    |                |
   | gender   | varchar(6)  | YES  |     | NULL    |                |
   | password | varchar(10) | YES  |     | NULL    |                |
   | doj      | date        | YES  |     | NULL    |                |
   | amount   | float(10,2) | YES  |     | NULL    |                |
   | ldate    | date        | YES  |     | NULL    |                |
   +----------+-------------+------+-----+---------+----------------+
   7 rows in set (0.00 sec)
   
   mysql> alter table main_tab drop ldate;
   Query OK, 11 rows affected (0.10 sec)
   Records: 11  Duplicates: 0  Warnings: 0
   
   mysql> desc main_tab;
   +----------+-------------+------+-----+---------+----------------+
   | Field    | Type        | Null | Key | Default | Extra          |
   +----------+-------------+------+-----+---------+----------------+
   | acc_no   | int(5)      | NO   | PRI | NULL    | auto_increment |
   | name     | varchar(20) | YES  |     | NULL    |                |
   | gender   | varchar(6)  | YES  |     | NULL    |                |
   | password | varchar(10) | YES  |     | NULL    |                |
   | doj      | date        | YES  |     | NULL    |                |
   | amount   | float(10,2) | YES  |     | NULL    |                |
   +----------+-------------+------+-----+---------+----------------+
   6 rows in set (0.00 sec)
   
   
   how to change a column without deleting the contents in mysql table