Mysql 第五天 查询数据

5.1 查询所有字段 5.2 查询指定字段

SELECT id,stuName,age,sex,gradeName FROM t_student ;

SELECT stuName,id,age,sex,gradeName FROM t_student ;

SELECT * FROM t_student;



5.3 where 条件查询

SELECT * FROM t_student WHERE id=1;

SELECT * FROM t_student WHERE age>22;



5.4 带in关键字查询

SELECT * FROM t_student WHERE age IN (21,23);

SELECT * FROM t_student WHERE age NOT IN (21,23);



5.5 带between and 关键字查询

SELECT * FROM t_student WHERE age BETWEEN 21 AND 24;

SELECT * FROM t_student WHERE age NOT BETWEEN 21 AND 24;



5.6 带like的模糊查询

SELECT * FROM t_student WHERE stuName LIKE '张三';

SELECT * FROM t_student WHERE stuName LIKE '张三%';

SELECT * FROM t_student WHERE stuName LIKE '张三__';

SELECT * FROM t_student WHERE stuName LIKE '%张三%';

5.7 空值查询

SELECT * FROM t_student WHERE sex IS NULL;

SELECT * FROM t_student WHERE sex IS NOT NULL;

5.8 带and 的多条件查询

SELECT * FROM t_student WHERE gradeName='一年级' AND age=23

5.9 带or的条件查询

SELECT * FROM t_student WHERE gradeName='一年级' OR age=23

5.10 带distinct的重复查询

SELECT DISTINCT gradeName FROM t_student;

5.11 对查询结果进行排序

SELECT * FROM t_student ORDER BY age ASC;

SELECT * FROM t_student ORDER BY age DESC;

5.12 group by分组查询

1. 单独使用

SELECT * FROM t_student GROUP BY gradeName;

2. group concat一起使用

SELECT gradeName,GROUP_CONCAT(stuName) FROM t_student GROUP BY gradeName;

3.与聚合函数一起使用

SELECT gradeName,COUNT(stuName) FROM t_student GROUP BY gradeName;

4.与having一起使用

SELECT gradeName,COUNT(stuName) FROM t_student GROUP BY gradeName HAVING COUNT(stuName)>3;

5.与with rollup一起使用 (最后一行总和)

SELECT gradeName,COUNT(stuName) FROM t_student GROUP BY gradeName WITH ROLLUP;

SELECT gradeName,GROUP_CONCAT(stuName) FROM t_student GROUP BY gradeName WITH ROLLUP;

5.13 limit分页

SELECT * FROM t_student LIMIT 0,5;

SELECT * FROM t_student LIMIT 5,5;

SELECT * FROM t_student LIMIT 10,5;