- mysql 修改一列自增长
set @rownum=0;
update a
SET id = (
select @rownum := @rownum +1 as nid)
WHERE id < 10;
l mysql 查询重复数据及其条数
select login_name,count(*) as count from sys_user group by login_name having count>1;
- l mysql 查询一个表中没有存在在另一个表的数据
SELECT * FROM A WHERE id NOT IN ( SELECT id FROM B);或者SELECT * FROM A WHERE NOT EXISTS ( SELECT 1 FROM B WHERE B.id = A.id );或者SELECT A.* FROM A LEFT JOIN B ON (A.id = B.id) WHERE b.id IS NULL
1.添加PRIMARY KEY（主键索引）
mysql>ALTER TABLE `table_name` ADD PRIMARY KEY ( `column` )
2.添加UNIQUE(唯一索引)
mysql>ALTER TABLE `table_name` ADD UNIQUE (
`column`
)
3.添加INDEX(普通索引)
mysql>ALTER TABLE `table_name` ADD INDEX index_name ( `column` )
4.添加FULLTEXT(全文索引)
mysql>ALTER TABLE `table_name` ADD FULLTEXT ( `column`)
5.添加多列索引
mysql>ALTER TABLE `table_name` ADD INDEX index_name ( `column1`, `column2`, `column3` )
- l 选择查询样例
<choose>
<when test="1==type">
<if test="0==chilId">
select id resourceId,cmdb_app_id cmdbId,cmdb_app_name cmdbApplicationName,third_id chilId,type,
third_name otherApplicationName, create_time createTime from third_cmdb_mapping where type = #{type}
<if test=" null!= cmdbApplicationName and '' !=cmdbApplicationName">
and cmdb_app_name like CONCAT('%',trim('${cmdbApplicationName}'),'%')
</if>
<if test=" null!= otherApplicationName and '' !=otherApplicationName">
and third_name like CONCAT('%',trim('${otherApplicationName}'),'%')
</if>
</if>
l <if test="1==chilId">
SELECT A.resource_id resourceId,A.pro_value cmdbApplicationName FROM cmdb_resource A
WHERE A.pro_key = 'CINAME' and A.resource_type = 'APPLICATION' and A.resource_id NOT IN ( SELECT B.cmdb_app_id FROM third_cmdb_mapping B where type =#{type})
<if test=" null!= cmdbApplicationName and '' !=cmdbApplicationName">
and pro_value like CONCAT('%',trim('${cmdbApplicationName}'),'%')
</if>
<if test=" null!= otherApplicationName and '' !=otherApplicationName">
and 1=2
</if>
</if>
</when>
</choose>
- l 查询时给某列赋值
select u.id,u.name,
(case u.sex
when 1 then '男'
when 2 then '女'
else '空的'
end )性别
from users u;
- case 第二种用法 判断 条件在when开始写
-
select ENAME,job,(case
when sal<500 then '低级员工'
when 500<sal and sal<1000 then '中级员工'
when sal >1000 then '高级员工'
else '' else 可以不写
end) jibei
from emp; - l mysql 模糊查询 去除空格
<if test=" null!= cmdbApplicationName and '' !=cmdbApplicationName">
and cmdb_app_name like CONCAT('%',trim('${cmdbApplicationName}'),'%')
</if>
练习sql
1、 查询Student表中的所有记录的Sname、Ssex和Class列。
select s.sname name,s.ssex sex,s.class class from students s;
2、 查询教师所有的单位即不重复的Depart列。
select DISTINCT (t.depart) depart from teachers t;
3、 查询Student表的所有记录。
select * from students;
4、 查询Score表中成绩在60到80之间的所有记录。
select * from scores where degree BETWEEN 60 and 80;
5、 查询Score表中成绩为85，86或88的记录。
select * from scores where degree in ('85','86','88');
6、 查询Student表中“95031”班或性别为“女”的同学记录。
select * from students s where s.class = '95031' or s.ssex ='女'
7、 以Class降序查询Student表的所有记录。
select * from students ORDER BY class desc;
8、 以Cno升序、Degree降序查询Score表的所有记录。
select * from scores s ORDER BY s.cno asc,s.degree desc;
9、 查询“95031”班的学生人数。
select COUNT(1) from students s where s.class = '95031'
10、查询Score表中的最高分的学生学号和课程号。
select s.cno cno,s.sno sno from scores s ORDER BY s.degree desc LIMIT 1;
11、查询‘3-105’号课程的平均分。
select s.cno, Avg(s.degree) avg
from scores s ORDER BY s.cno and s.cno = '3-105';
12、查询Score表中至少有5名学生选修的并以3开头的课程的平均分数。
select s.sno,AVG(degree) from scores s WHERE s.cno like '3%' group by s.cno HAVING COUNT(s.sno) >= 5;
13、查询最低分大于70，最高分小于90的Sno列。
SELECT Sno
FROM Scores
GROUP BY Sno
HAVING MAX(Degree)<90 AND MIN(Degree)>70;
14、查询所有学生的Sname、Cno和Degree列。
select s.sname,c.cno,c.degree from students s inner join scores c on s.sno = c.sno ORDER BY s.sname
15、查询所有学生的Sno、Cname和Degree列。
select a.sno,b.degree,c.cname from test.students a,test.scores b,test.courses c where a.sno = b.sno and c.cno = b.cno;
16、查询所有学生的Sname、Cname和Degree列。
select a.sname,b.degree,c.cname from test.students a,test.scores b,test.courses c where a.sno = b.sno and c.cno = b.cno;
17、查询“95033”班所选课程的平均分。
SELECT Cname,AVG(Degree)
FROM Students INNER JOIN Scores
ON(Students.Sno=Scores.Sno) INNER JOIN Courses
ON(Scores.Cno=Courses.Cno)
WHERE Class='95033'
GROUP BY Courses.Cno
ORDER BY Cname;
18、假设使用如下命令建立了一个grade表：
create table grade(low number(3,0),upp number(3),rank char(1));
insert into grade values(90,100,’A’);
insert into grade values(80,89,’B’);
insert into grade values(70,79,’C’);
insert into grade values(60,69,’D’);
insert into grade values(0,59,’E’);
commit;
现查询所有同学的Sno、Cno和rank列。
SELECT Sno,Cno,rank
FROM Scores INNER JOIN grade
ON(Scores.Degree>=grade.low AND Scores.Degree<=grade.upp)
ORDER BY Sno;
19、查询选修“3-105”课程的成绩高于“109”号同学成绩的所有同学的记录。
--标准答案
SELECT s1.Sno,s1.Degree
FROM Scores AS s1 INNER JOIN Scores AS s2
ON(s1.Cno=s2.Cno AND s1.Degree>s2.Degree)
WHERE s1.Cno='3-105' AND s2.Sno='109'
ORDER BY s1.Sno;
--自己写的垃圾sql
SELECT * FROM students inner join scores on students.sno = scores.sno inner join courses on courses.cno = scores.cno where courses.cno = '3-105' and scores.degree > ( select degree from students inner join scores on students.sno =scores.sno inner join courses on courses.cno = scores.cno where students.sno='109' and courses.cno = '3-105') order by students.sno;
20、查询score中选学一门以上课程的同学中分数为非最高分成绩的记录。
SELECT *
FROM Scores
GROUP BY Sno
HAVING COUNT(cno)>1 AND Degree!=MAX(Degree);
21、查询成绩高于学号为“109”、课程号为“3-105”的成绩的所有记录。
--标准答案
SELECT s1.Sno,s1.Degree
FROM Scores AS s1 INNER JOIN Scores AS s2
ON(s1.Cno=s2.Cno AND s1.Degree>s2.Degree)
WHERE s1.Cno='3-105' AND s2.Sno='109'
ORDER BY s1.Sno;
--垃圾sql
select * from scores a where a.degree>(
select b.degree from scores b where b.sno ='109' and b.cno = '3-105'
) order by a.sno
22、查询和学号为108的同学同年出生的所有学生的Sno、Sname和Sbirthday列。
select s1.sno,s1.sname,s1.sbirthday from students s1 inner join students s2
on (YEAR(s1.sbirthday) = YEAR(s2.sbirthday)) where s1.sno='108'
23、查询“张旭“教师任课的学生成绩。
SELECT Sno,Degree
FROM Scores INNER JOIN Courses
ON(Scores.Cno=Courses.Cno) INNER JOIN Teachers
ON(Courses.Tno=Teachers.Tno)
WHERE Teachers.Tname='张旭';
24、查询选修某课程的同学人数多于5人的教师姓名。
--自己写的还算凑合
select t.tname from courses c
inner join teachers t
on c.tno = t.tno
inner join scores e
on e.cno = c.cno
inner join students s
on s.sno = e.sno
group by c.cno
HAVING COUNT(s.sno)>=5;
--标准答案
SELECT DISTINCT Tname
FROM Scores INNER JOIN Courses
ON(Scores.Cno=Courses.Cno) INNER JOIN Teachers
ON(Courses.Tno=Teachers.Tno)
WHERE Courses.Cno IN(SELECT Cno FROM Scores GROUP BY(Cno) HAVING COUNT(Sno)>5);
25、查询95033班和95031班全体学生的记录。
SELECT *
FROM Students
WHERE Class IN ('95033','95031')
ORDER BY Class;
26、查询存在有85分以上成绩的课程Cno.
SELECT DISTINCT Cno
FROM Scores
WHERE Degree>85;
27、查询出“计算机系“教师所教课程的成绩表。
select c.degree from courses a
inner join teachers b
on a.tno = b.tno
inner join scores c
on c.cno = a.cno
where b.depart = '计算机系'
28、查询“计算机系”与“电子工程系“不同职称的教师的Tname和Prof。
--标准答案
SELECT Tname,Prof
FROM Teachers
WHERE Depart='计算机系' AND Prof NOT IN(
SELECT DISTINCT Prof
FROM Teachers
WHERE Depart='电子工程系');
--垃圾答案
select DISTINCT(prof) from teachers
where depart= '计算机系' or depart= '电子工程系'
GROUP BY prof
29、查询选修编号为“3-105“课程且成绩至少高于选修编号为“3-245”的同学的Cno、Sno和Degree,并按Degree从高到低次序排序。
SELECT Cno,Sno,Degree
FROM Scores
WHERE Cno='3-105' AND Degree > ANY(
SELECT Degree
FROM Scores
WHERE Cno='3-245')
ORDER BY Degree DESC;
30、查询选修编号为“3-105”且成绩高于选修编号为“3-245”课程的同学的Cno、Sno和Degree.
SELECT Cno,Sno,Degree
FROM Scores
WHERE Cno='3-105' AND Degree > ALL(
SELECT Degree
FROM Scores
WHERE Cno='3-245')
ORDER BY Degree DESC;
31、查询所有教师和同学的name、sex和birthday.
SELECT Sname,Ssex,Sbirthday FROM Students UNION SELECT Tname,Tsex,Tbirthday FROM Teachers;
32、查询所有“女”教师和“女”同学的name、sex和birthday.
SELECT Sname,Ssex,Sbirthday FROM Students WHERE Ssex='女' UNION SELECT Tname,Tsex,Tbirthday FROM Teachers WHERE Tsex='女';
33、查询成绩比该课程平均成绩低的同学的成绩表。
SELECT s1.*
FROM Scores AS s1 INNER JOIN (
SELECT Cno,AVG(Degree) AS aDegree
FROM Scores
GROUP BY Cno) s2
ON(s1.Cno=s2.Cno AND s1.Degree<s2.aDegree);
34、查询所有任课教师的Tname和Depart.
SELECT Tname,Depart FROM Teachers WHERE Tno IN( SELECT Tno FROM Courses );
35 查询所有未讲课的教师的Tname和Depart.
SELECT Tname,Depart FROM Teachers WHERE Tno NOT IN( SELECT Tno FROM Courses );
36、查询至少有2名男生的班号。
-- 自己代码 都可以
select * from students GROUP BY class HAVING COUNT(ssex) > 2
--提供sql
SELECT Class,COUNT(1) AS boyCount
FROM Students
WHERE Ssex='男'
GROUP BY Class
HAVING boyCount>=2;
37、查询Student表中不姓“王”的同学记录。
SELECT * FROM Students WHERE Sname NOT LIKE '王%';
38、查询Student表中每个学生的姓名和年龄。
select YEAR(NOW()) -YEAR(sbirthday) from students
39、查询Student表中最大和最小的Sbirthday日期值。
SELECT MIN(Sbirthday),MAX(Sbirthday) FROM Students;
40、以班号和年龄从大到小的顺序查询Student表中的全部记录。
SELECT * FROM Students ORDER BY Class DESC,Sbirthday ASC;
41、查询“男”教师及其所上的课程。
select * from teachers inner join courses on teachers.tno = courses.tno where teachers.tsex = '男'
42、查询最高分同学的Sno、Cno和Degree列。
SELECT *
FROM Scores
GROUP BY Cno
HAVING Degree=Max(Degree);
43、查询和“李军”同性别的所有同学的Sname.
SELECT s1.Sname
FROM Students AS s1 INNER JOIN Students AS s2
ON(s1.Ssex=s2.Ssex)
WHERE s2.Sname='李军';
44、查询和“李军”同性别并同班的同学Sname.
SELECT s1.Sname
FROM Students AS s1 INNER JOIN Students AS s2
ON(s1.Ssex=s2.Ssex and s1.class=s2.class)
WHERE s2.Sname='李军';
45、查询所有选修“计算机导论”课程的“男”同学的成绩表
--自己写的ok代码
select * from courses a inner join scores b
on a .cno = b.cno inner join students c
on b.sno= c.sno
WHERE a.cname = '计算机导论' and c.ssex = '男';
--提供答案
SELECT *
FROM Scores
WHERE Sno IN (
SELECT Sno
FROM Students
WHERE Ssex='男') AND
Cno IN (
SELECT Cno
FROM Courses
WHERE Cname='计算机导论');