标签：函数 where arch 名称 desc sel asc show 指定
单表查询
查询所有列
1 SELECT * FROM product;
查询指定列
1 SELECT pro_name,price,pinpai FROM product;
添加常量列
1 SELECT pro_name AS ‘产品名称‘,price FROM product;
创建学生表
1 CREATE TABLE stu( 2 sid INT, 3 sname VARCHAR(10), 4 sex VARCHAR(2), 5 servlet DOUBLE, 6 jsp DOUBLE, 7 html DOUBLE 8 ) 9 SHOW TABLES; 10 INSERT INTO stu VALUES(1,‘佩奇‘,‘女‘,100,60,80); 11 INSERT INTO stu VALUES(2,‘乔治‘,‘男‘,25,58,100); 12 INSERT INTO stu VALUES(3,‘薛之谦‘,‘男‘,100,100,100); 13 INSERT INTO stu VALUES(4,‘李荣浩‘,‘男‘,90,90,90); 14 INSERT INTO stu(sid,sname,servlet,html) VALUES(5,‘于文文‘,90,90); 15 INSERT INTO stu(sid,sname,servlet,html) VALUES(6,‘‘,90,10); 16 SELECT * FROM stu;
查询时合并列
1 SELECT sname,(servlet+jsp+html) AS ‘总成绩‘ FROM stu;
查询时去除重复记录
1 SELECT DISTINCT sex FROM stu;
条件查询
1 SELECT * FROM stu WHERE sex=‘男‘ AND sname=‘薛之谦‘; 2 SELECT * FROM stu WHERE sex=‘女‘ OR sname=‘薛之谦‘;
查询大于70分的学生
1 SELECT * FROM stu WHERE servlet>60;
查询jsp成绩不等于60分的学生
1 SELECT * FROM stu WHERE jsp<>60;
查询html成绩在60和100之间的学生
1 SELECT * FROM stu WHERE html BETWEEN 60 AND 100; 2 SELECT * FROM stu WHERE html >= 60 AND html<=100;
查询sex为null的学生
1 SELECT * FROM stu WHERE sex IS NULL; 2 SELECT * FROM stu WHERE sex IS NOT NULL;
查询sname是空字符串的学生
1 SELECT * FROM stu WHERE sname=‘‘; 2 SELECT * FROM stu WHERE sname<>‘‘;
查询sex不为空的学生
1 SELECT * FROM stu WHERE sex IS NOT NULL AND sex<>‘‘;
查询所有产品中带有索尼的产品
1 SELECT * FROM product WHERE pro_name LIKE ‘%索尼%‘;
查询班级中所有两个字的同学
1 SELECT * FROM stu WHERE sname LIKE ‘__‘;
聚合函数：查询stu表中所有学生的servlet总成绩
1 SELECT SUM(servlet) FROM stu;
聚合函数：查询stu表中所有学生的servlet平均成绩
1 SELECT AVG(servlet) FROM stu;
聚合函数：查询stu表中jsp课程中的最高分
1 SELECT MAX(JSP) FROM stu;
最低分
1 SELECT MIN(jsp) FROM stu;
查询stu表中有多少人
1 SELECT COUNT(*) FROM stu;（每列统计 取最大值）
分页
1 SELECT * FROM stu LIMIT 0,2;
查询排序
1 SELECT * FROM stu ORDER BY html ASC;（升序） 2 SELECT * FROM stu ORDER BY html DESC;(倒序)
查询stu表中所有男同学的html成绩排序
1 SELECT * FROM stu WHERE sex=‘男‘ ORDER BY html; 2 SELECT * FROM stu ORDER BY jsp ASC,html DESC;
查询男女人数
1 SELECT sex,COUNT(*) FROM stu GROUP BY sex;
查询总人数大于2的性别
1 SELECT SEX,COUNT(*) FROM STU GROUP BY sex HAVING COUNT(*)>2;
标签：函数 where arch 名称 desc sel asc show 指定
原文地址：https://www.cnblogs.com/2734156755z/p/9290168.html
