DQL_条件查询

DQL 条件查询

SELECT * FROM student WHERE age=22 OR age=18 OR age=25
SELECT * FROM student WHERE age IN(22,18,25);

–查询英语成绩为NULL

SELECT * FROM student WHERE english = NULL; --错误，null 值不能使用=（！=）判断

以下是正确的

SELECT * FROM student WHERE english IS NULL

– 查询英语成绩不是NULL

SELECT * FROM student WHERE english IS NOT NULL;