mysql 数据库 内容的增删改查

/*所有字段插入值*//*注意插入值数目要与字段值一致*/
INSERT INTO student VALUES(1,'熊大','123','2019-10-18',1200);
INSERT INTO student VALUES(3,'熊二','123','2019-10-18',1200);
/*部分字段插入值*/
INSERT  INTO student (uid,PASSWORD, money)VALUES(2,'123456',10000);
/*修改语句*/
UPDATE student SET uname='熊二' WHERE uid=2;
UPDATE student SET PASSWORD='123456' WHERE uname='熊二';
/*修改多个逗号分隔*/
UPDATE student SET uname='琪琪国王',PASSWORD='admin'WHERE uid=1;
UPDATE student SET birth='2019/11/29'WHERE uid=2;

*不带条件的删除：全表删除 能回滚 只能删除数据不删约束*/
DELETE FROM student
/*带条件的删除*/
DELETE FROM student WHERE uid=3
/*全表删除 不能回滚 数据约束全删*/
TRUNCATE TABLE student

/*查询所有数据*/
SELECT *FROM student;

/*查询指定字段的值*/
SELECT uname,PASSWORD FROM student

/*查询时添加常量列*/
SELECT uname AS n,PASSWORD AS p FROM student

/*查询时合并列*/
SELECT sname,(html+js+jquery)/3 AS savg FROM score

/*查询时保留小数位数*/
SELECT sname,FORMAT(html,3) AS html FROM score

/*查询时对某个字段的值进行去重*/
/*查询所有同学所在的班级都有那几个班级*/
SELECT DISTINCT sclass FROM score
SELECT DISTINCT(sclass) FROM score

/*条件查询*/
/*查询所有女生的所有信息*/
SELECT * FROM score WHERE sex='女'
/*查询所有男生的姓名，html成绩和jquery成绩*/
SELECT sname,html,jquery FROM score WHERE sex='男'
/*查询外婆在哪个班*/
SELECT sclass FROM score WHERE sname='外婆'
/*查询所有js成绩不合格的同学的姓名*/
SELECT sname FROM score WHERE js<60

/*查询jquery成绩合格的所有女同学信息*/
SELECT * FROM score WHERE jquery>=60 AND sex='女'
/*查询所有html成绩不合格的男同学姓名*/
SELECT sname FROM score WHERE html<60 AND sex='男'

/*查询js成绩合格或者是html成绩合格的同学信息*/
SELECT * FROM score WHERE js>=60 OR html>=60
/*查询性别为男或者是java1018的同学姓名*/

SELECT * FROM score WHERE js>=60 OR html>=60;

/*不等于 <> !=*/
SELECT * FROM score WHERE html<>10;

/*查询HTML成绩在70-100之间同学信息 包头包尾`student``student`*/
SELECT * FROM score WHERE html BETWEEN 70 AND 100;

/*查询学生表中 姓名不为空的学生信息*/
SELECT * FROM student WHERE uname<>'' AND uname IS NOT NULL;
/*查询学生表中 mima为空的学生信息*/
SELECT * FROM student WHERE PASSWORD='' OR PASSWORD IS NULL;

/*查询score表中性大的信息*/
SELECT * FROM score WHERE sname LIKE '大%';
/*查询score表中性大两个的信息*/
SELECT * FROM score WHERE sname LIKE '大_';
/*查询score表中性两个的信息*/
SELECT * FROM score WHERE sname LIKE '__';

/*查询score表java1018 js 总成绩*/
SELECT SUM(js)AS js总成绩 FROM score WHERE sclass='java1018';
/*查询score表java0723 html 平均成绩*/
SELECT FORMAT(AVG(html),2) FROM score WHERE sclass='java0723';
/*查询score表java1018 jquery最高分*/
SELECT MAX(jquery) FROM score WHERE sclass='java1018';
/*查询score表所有学生总成绩的最低分*/
SELECT MIN(IFNULL(jquery,0)+IFNULL(js,0)+IFNULL(html,0)) FROM score;
/*查询score本班有多少人  COUNT(*)原理是把每一列都统计一下取最大值*/
SELECT COUNT(*)FROM score;

/*查询本班有多少人*/
SELECT sname,COUNT(*) FROM score
-- 分页查询
-- 每页显示两条
-- 第一页 limit 起始行（从零开始），每页显示行数
-- 分页：limit(当前页-1)*每页显示的条数，每页显示的条数
SELECT * from score LIMIT 0,2;
/*第二页*/
SELECT * from score LIMIT 2,2;
/*第三页*/
SELECT * from score LIMIT 4,2;

-- 排序放到最后
-- 查询所有同学信息并且按照js成绩从大到小排
SELECT *from score ORDER BY js desc;
SELECT *from score ORDER BY js asc;
SELECT *from score ORDER BY js;
-- 查询所有同学信息并且按照js成绩从大到小排 jquery成绩正序
SELECT *from score ORDER BY js desc,jquery asc;

-- 查询男女的人数
select sex,COUNT(*) FROM score  GROUP BY sex ORDER BY COUNT(*);
--查询每个性别的js总成绩
SELECT sex,SUM(js)FROM score  GROUP BY sex ORDER BY sum(js);

--查询哪个性别的js高于60分总成绩
SELECT sex,SUM(js)FROM score  GROUP BY sex HAVING sum(js)>60 ;
SELECT sex,SUM(js)as tt FROM score  GROUP BY sex HAVING tt>60;

--查询java1018班每个性别的js总成绩且高于60分
SELECT sex,SUM(js)FROM score WHERE sclass='java1018' GROUP BY sex HAVING sum(js)>=60 ;

-- 查询那个姓别的人数大于一
SELECT sex,sum(js),sum(jquery),sum(html)FROM score GROUP BY sex;
SELECT sex FROM score GROUP BY sex HAVING sex<>'女'and count(*)>1;
SELECT SUM(IFNULL(js,0))AS js总成绩 FROM score WHERE sclass='java1018';