mysql不等於null和等於null的寫法

1.表結構 

2.表數據

 3.查詢teacher_name字段不能等於空並且也不能等於空字符

SELECT * FROM sys_teacher WHERE teacher_name IS NOT NULL AND teacher_name <>''

查詢結果：

4.查詢teacher_name字段等於null或等於空字符

SELECT * FROM sys_teacher WHERE teacher_name = '' OR teacher_name IS NULL

查詢結果：