问题遇到的现象和发生背景
select * FROM courses where NOT teacher_id = 3 and student_count > 800 和select * FROM courses where NOT (teacher_id = 3 and student_count <= 800 ) 我想问下这两个的处理逻辑不一样吗
select * FROM courses where NOT teacher_id = 3 and student_count > 800 和select * FROM courses where NOT (teacher_id = 3 and student_count <= 800 ) 我想问下这两个的处理逻辑不一样吗
not 貌似一般不单独用的吧?
加了括号就对括号里的判断取反
不加则对not 后面的第一个字段生效