非空约束2(CHAR(2)数据太小会出错)
ALTER TABLE books MODIFY title VARCHAR(50) NOT NULL;blog
---取消非空
ALTER TABLE books MODIFY title VARCHAR(50) NULL;it
ALTER TABLE books MODIFY sex CHAR(2) NOT NULL;im
Data truncated for column 'sex' at row 1数据
CHAR(2)数据太小会出错img