MySQL中ALTER TABLE的正确语法是什么？

Question

I am trying to add a simple column in my table in MySQL but it is giving syntax error:

Error Code: 1064

You have an error in your SQL syntax;

Code:

ALTER TABLE `user`
ADD classname VARCHAR 150 NULL AFTER id;

Answer 1

try:

ALTER TABLE `user`
ADD classname VARCHAR(150) NULL AFTER id;

Answer 2

The length of the varchar type must be enclosed by brackets:

ALTER TABLE `user`
ADD classname VARCHAR(150) NULL AFTER id;

Answer 3

the length of a field n sql must be enclosed with (),but you have missed the paranthesis(),so you were getting the error,just try with ()

ALTER TABLE `user`
ADD classname VARCHAR(150) NULL AFTER id;

Answer 4

extra parenthesis is required for datatype

ALTER TABLE `user`
ADD classname VARCHAR(150) NULL AFTER id;