MYSQL have set a column to not null but still it's accepting null value [duplicate]

Try this:

ALTER TABLE tablename 
MODIFY COLUMN name VARCHAR(255) CHARACTER SET utf8 COLLATE utf8_persian_ci NOT NULL CHECK (name <> '');

DEMO:

mysql> create table tablename(id int(2) not null, something varchar(25) null, primary key(id));
Query OK, 0 rows affected (0.15 sec)
mysql> insert into tablename values(0,'hello');
Query OK, 1 row affected (0.38 sec)

mysql> insert into tablename values(1,'salut');
Query OK, 1 row affected (0.31 sec)

mysql> select * from tablename;
+----+-----------+
| id | something |
+----+-----------+
|  0 | hello     |
|  1 | salut     |
+----+-----------+
2 rows in set (0.00 sec)

Now, I run the UPDATE command:

mysql> ALTER TABLE tablename  MODIFY COLUMN something VARCHAR(255) CHARACTER SET utf8 COLLATE utf8_persian_ci NOT NULL;
Query OK, 2 rows affected (0.70 sec)
Records: 2  Duplicates: 0  Warnings: 0

I insert a normal row:

mysql> insert into tablename values(2,'france');
Query OK, 1 row affected (0.29 sec)

But it does not allow me to insert a NULL value:

mysql> insert into tablename values(3,NULL);
ERROR 1048 (23000): Column 'something' cannot be null

I check to be sure:

mysql> select * from tablename;
+----+-----------+
| id | something |
+----+-----------+
|  0 | hello     |
|  1 | salut     |
|  2 | france    |
+----+-----------+
3 rows in set (0.00 sec)