mysql-数据查询

CREATE TABLE class0328(
          id INT,
          cname VARCHAR(20),
          sex VARCHAR(2),
          age INT,
          birthday DATE,
          score DOUBLE,
          html DOUBLE,
          js DOUBLE
          );
DESC class0328;
DROP TABLE class0328
INSERT INTO class0328 VALUES(1,'董斌','男',25,'1993-09-13',80,20,60);
INSERT INTO class0328 VALUES(2,'张锐','男',25,'1993-09-25',81,31,50);
INSERT INTO class0328 VALUES(3,'王荣臣','男',23,'1996-07-07',30,50,30);
INSERT INTO class0328 VALUES(4,'韩凯','男',26,'1991-05-20',25,20,70);
INSERT INTO class0328 VALUES(5,'张禄','男',26,'1991-03-02',60,60,30);
INSERT INTO class0328 VALUES(6,'刘继勋','男',24,'1994-11-27',0.5,90,60);
INSERT INTO class0328 VALUES(7,'张维','男',29,'1989-02-24',100,20,79);
INSERT INTO class0328 VALUES(8,'牛攀','男',29,'1989-12-24',100,50,70);
INSERT INTO class0328 VALUES(9,'王祖贤','女',19,'20000101',100,50,20);
INSERT INTO class0328 VALUES(10,'刘亦菲','',21,'20050201',99,60,30);
INSERT INTO class0328(id,cname,sex,age) VALUES(11,'迪丽热巴','女',25);
/*查询所有列*/
SELECT * FROM class0328;
/*查询指定列*/
SELECT cname,sex FROM class0328;
/*查询时添加常量列*/
SELECT cname AS '姓名',sex AS '性别' FROM class0328;
/*查询时合并列*/
SELECT cname,(html+js) AS '总成绩' FROM class0328;
/*查询时去除重复记录*/
SELECT DISTINCT sex FROM class0328;
/*条件查询*/
SELECT * FROM class0328 WHERE id=1 AND sex='男';
SELECT * FROM class0328 WHERE sex='女' OR age=25;
SELECT cname FROM class0328 WHERE html>60;
SELECT * FROM class0328 WHERE html<>60;
SELECT * FROM class0328 WHERE html>=20 AND html<=60;
SELECT * FROM class0328 WHERE html BETWEEN 20 AND 60;
/*判空条件*/
SELECT * FROM class0328 WHERE html IS NULL;
SELECT * FROM class0328 WHERE html IS NOT NULL;
SELECT * FROM class0328 WHERE sex='';
SELECT * FROM class0328 WHERE sex<>'';
SELECT * FROM class0328 WHERE html IS NULL OR sex='';
SELECT * FROM class0328 WHERE html IS NOT NULL AND sex<>'';
/*模糊条件*/
SELECT * FROM class0328 WHERE cname LIKE '王%';
SELECT * FROM class0328 WHERE cname LIKE '王__';
/*聚合查询*/
SELECT SUM(html) FROM class0328;
SELECT SUM(html) AS 'HTML总成绩' FROM class0328;
SELECT SUM(html + js) FROM class0328;
SELECT AVG(html) AS 'HTML平均' FROM class0328;
SELECT MAX(js) AS '最大值' FROM class0328;
SELECT MIN(js) AS '最小值' FROM class0328;
SELECT cname,MIN(js) AS '最小值' FROM class0328;
SELECT COUNT(*) FROM class0328;
SELECT COUNT(sex) FROM class0328;
SELECT COUNT(html) FROM class0328;
/*分页查询*/
SELECT * FROM class0328 LIMIT 0,2;
SELECT * FROM class0328 LIMIT 2,2;
SELECT * FROM class0328 LIMIT 4,2;
SELECT * FROM class0328 LIMIT 6,2;
SELECT * FROM class0328 LIMIT 8,2;
SELECT * FROM class0328 LIMIT 10,2;
/*查询排序*/
SELECT * FROM class0328 ORDER BY html ASC;
SELECT * FROM class0328 ORDER BY html DESC;
SELECT * FROM class0328 ORDER BY html ASC,js DESC;
/*分组查询*/
SELECT sex,COUNT(sex) FROM class0328 GROUP BY sex;
SELECT html,COUNT(*) FROM class0328 GROUP BY html HAVING html>60;
SELECT sex,COUNT(*) FROM class0328 GROUP BY sex HAVING COUNT(*)>2;