check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 4这是什么错误，检查了很多遍，都没成功，谢谢
mysql> CREATE TABLE tb5(
-> id SMALLINT UNSIGNED PRIMARY KEY,
-> username VARCHAR(20) NOT NULL,
-> );
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 4
