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数据库常用sql语句有哪些

时间:2022-03-18 09:00:02 SQL 我要投稿

数据库常用sql语句有哪些

  结构化查询语言简称SQL,是一种特殊目的的编程语言,是一种数据库查询和程序设计语言,用于存取数据以及查询、更新和管理关系数据库系统。下面是小编整理的数据库常用sql语句有哪些,欢迎大家分享。

  数据库常用sql语句

  Student(S#,Sname,Sage,Ssex) 学生表

  Course(C#,Cname,T#) 课程表

  SC(S#,C#,score) 成绩表

  Teacher(T#,Tname) 教师表

  问题:

  1、查询“001”课程比“002”课程成绩高的所有学生的学号;

  select a.S# from (select s#,score from SC where C#='001') a,(select s#,score

  from SC where C#='002') b

  where a.score>b.score and a.s#=b.s#;

  2、查询平均成绩大于60分的同学的学号和平均成绩;

  select S#,avg(score)

  from sc

  group by S# having avg(score) >60;

  3、查询所有同学的学号、姓名、选课数、总成绩;

  select Student.S#,Student.Sname,count(SC.C#),sum(score)

  from Student left Outer join SC on Student.S#=SC.S#

  group by Student.S#,Sname

  4、查询姓“李”的老师的个数;

  select count(distinct(Tname))

  from Teacher

  where Tname like '李%';

  5、查询没学过“叶平”老师课的同学的学号、姓名;

  select Student.S#,Student.Sname

  from Student

  where S# not in (select distinct( SC.S#) from SC,Course,Teacher where SC.C#=Course.C# and Teacher.T#=Course.T# and Teacher.Tname='叶平');

  6、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名;

  select Student.S#,Student.Sname from Student,SC where Student.S#=SC.S# and SC.C#='001'and exists( Select * from SC as SC_2 where SC_2.S#=SC.S# and SC_2.C#='002');

  7、查询学过“叶平”老师所教的所有课的同学的学号、姓名;

  select S#,Sname

  from Student

  where S# in (select S# from SC ,Course ,Teacher where SC.C#=Course.C# and Teacher.T#=Course.T# and Teacher.Tname='叶平' group by S# having count(SC.C#)=(select count(C#) from Course,Teacher where Teacher.T#=Course.T# and Tname='叶平'));

  8、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名;

  Select S#,Sname from (select Student.S#,Student.Sname,score ,(select score from SC SC_2 where SC_2.S#=Student.S# and SC_2.C#='002') score2

  from Student,SC where Student.S#=SC.S# and C#='001') S_2 where score2<score;

  9、查询所有课程成绩小于60分的同学的学号、姓名;

  select S#,Sname

  from Student

  where S# not in (select Student.S# from Student,SC where S.S#=SC.S# and score>60);

  10、查询没有学全所有课的同学的学号、姓名;

  select Student.S#,Student.Sname

  from Student,SC

  where Student.S#=SC.S# group by Student.S#,Student.Sname having count(C#) <(select count(C#) from Course);

  11、查询至少有一门课与学号为“1001”的同学所学相同的同学的学号和姓名;

  select S#,Sname from Student,SC where Student.S#=SC.S# and C# in select C# from SC where S#='1001';

  12、查询至少学过学号为“001”同学所有一门课的其他同学学号和姓名;

  select distinct SC.S#,Sname

  from Student,SC

  where Student.S#=SC.S# and C# in (select C# from SC where S#='001');

  13、把“SC”表中“叶平”老师教的课的成绩都更改为此课程的平均成绩;

  SC set score=(select avg(SC_2.score)

  from SC SC_2

  where SC_2.C#=SC.C# ) from Course,Teacher where Course.C#=SC.C# and Course.T#=Teacher.T# and Teacher.Tname='叶平');

  14、查询和“1002”号的同学学习的课程完全相同的其他同学学号和姓名;

  select S# from SC where C# in (select C# from SC where S#='1002')

  group by S# having count(*)=(select count(*) from SC where S#='1002');

  15、删除学习“叶平”老师课的SC表记录;

  Delect SC

  from course ,Teacher

  where Course.C#=SC.C# and Course.T#= Teacher.T# and Tname='叶平';

  16、向SC表中插入一些记录,这些记录要求符合以下条件:没有上过编号“003”课程的同学学号、2、

  号课的平均成绩;

  Insert SC select S#,'002',(Select avg(score)

  from SC where C#='002') from Student where S# not in (Select S# from SC where C#='002');

  17、按平均成绩从高到低显示所有学生的“数据库”、“企业管理”、“英语”三门的课程成绩,按如下形式显示: 学生ID,,数据库,企业管理,英语,有效课程数,有效平均分

  SELECT S# as 学生ID

  ,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='004') AS 数据库

  ,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='001') AS 企业管理

  ,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='006') AS 英语

  ,COUNT(*) AS 有效课程数, AVG(t.score) AS 平均成绩

  FROM SC AS t

  GROUP BY S#

  ORDER BY avg(t.score)

  18、查询各科成绩最高和最低的分:以如下形式显示:课程ID,最高分,最低分

  SELECT L.C# As 课程ID,L.score AS 最高分,R.score AS 最低分

  FROM SC L ,SC AS R

  WHERE L.C# = R.C# and

  L.score = (SELECT MAX(IL.score)

  FROM SC AS IL,Student AS IM

  WHERE L.C# = IL.C# and IM.S#=IL.S#

  GROUP BY IL.C#)

  AND

  R.Score = (SELECT MIN(IR.score)

  FROM SC AS IR

  WHERE R.C# = IR.C#

  GROUP BY IR.C#

  );

  19、按各科平均成绩从低到高和及格率的百分数从高到低顺序

  SELECT t.C# AS 课程号,max(course.Cname)AS 课程名,isnull(AVG(score),0) AS 平均成绩

  ,100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS 及格百分数

  FROM SC T,Course

  where t.C#=course.C#

  GROUP BY t.C#

  ORDER BY 100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) DESC

  20、查询如下课程平均成绩和及格率的百分数(用"1行"显示): 企业管理(001),马克思(002),OO&UML (003),数据库(004)

  SELECT SUM(CASE WHEN C# ='001' THEN score ELSE 0 END)/SUM(CASE C# WHEN '001' THEN 1 ELSE 0 END) AS 企业管理平均分

  ,100 * SUM(CASE WHEN C# = '001' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '001' THEN 1 ELSE 0 END) AS 企业管理及格百分数

  ,SUM(CASE WHEN C# = '002' THEN score ELSE 0 END)/SUM(CASE C# WHEN '002' THEN 1 ELSE 0 END) AS 马克思平均分

  ,100 * SUM(CASE WHEN C# = '002' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '002' THEN 1 ELSE 0 END) AS 马克思及格百分数

  ,SUM(CASE WHEN C# = '003' THEN score ELSE 0 END)/SUM(CASE C# WHEN '003' THEN 1 ELSE 0 END) AS UML平均分

  ,100 * SUM(CASE WHEN C# = '003' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '003' THEN 1 ELSE 0 END) AS UML及格百分数

  ,SUM(CASE WHEN C# = '004' THEN score ELSE 0 END)/SUM(CASE C# WHEN '004' THEN 1 ELSE 0 END) AS 数据库平均分

  ,100 * SUM(CASE WHEN C# = '004' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '004' THEN 1 ELSE 0 END) AS 数据库及格百分数

  FROM SC

  21、查询不同老师所教不同课程平均分从高到低显示

  SELECT max(Z.T#) AS 教师ID,MAX(Z.Tname) AS 教师姓名,C.C# AS 课程ID,MAX(C.Cname) AS 课程名称,AVG(Score) AS 平均成绩

  FROM SC AS T,Course AS C ,Teacher AS Z

  where T.C#=C.C# and C.T#=Z.T#

  GROUP BY C.C#

  ORDER BY AVG(Score) DESC

  22、查询如下课程成绩第 3 名到第 6 名的学生成绩单:企业管理(001),马克思(002),UML (003),数据库(004)

  [学生ID],[学生姓名],企业管理,马克思,UML,数据库,平均成绩

  SELECT DISTINCT top 3

  SC.S# As 学生学号,

  Student.Sname AS 学生姓名 ,

  T1.score AS 企业管理,

  T2.score AS 马克思,

  T3.score AS UML,

  T4.score AS 数据库,

  ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) as 总分

  FROM Student,SC LEFT JOIN SC AS T1

  ON SC.S# = T1.S# AND T1.C# = '001'

  LEFT JOIN SC AS T2

  ON SC.S# = T2.S# AND T2.C# = '002'

  LEFT JOIN SC AS T3

  ON SC.S# = T3.S# AND T3.C# = '003'

  LEFT JOIN SC AS T4

  ON SC.S# = T4.S# AND T4.C# = '004'

  WHERE student.S#=SC.S# and

  ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)

  NOT IN

  (SELECT

  DISTINCT

  TOP 15 WITH TIES

  ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)

  FROM sc

  LEFT JOIN sc AS T1

  ON sc.S# = T1.S# AND T1.C# = 'k1'

  LEFT JOIN sc AS T2

  ON sc.S# = T2.S# AND T2.C# = 'k2'

  LEFT JOIN sc AS T3

  ON sc.S# = T3.S# AND T3.C# = 'k3'

  LEFT JOIN sc AS T4

  ON sc.S# = T4.S# AND T4.C# = 'k4'

  ORDER BY ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) DESC);

  23、统计列印各科成绩,各分数段人数:课程ID,课程名称,[100-85],[85-70],[70-60],[<60]

  SELECT SC.C# as 课程ID, Cname as 课程名称

  ,SUM(CASE WHEN score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS [100 - 85]

  ,SUM(CASE WHEN score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS [85 - 70]

  ,SUM(CASE WHEN score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS [70 - 60]

  ,SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) AS [60 -]

  FROM SC,Course

  where SC.C#=Course.C#

  GROUP BY SC.C#,Cname;

  24、查询学生平均成绩及其名次

  SELECT 1+(SELECT COUNT( distinct 平均成绩)

  FROM (SELECT S#,AVG(score) AS 平均成绩

  FROM SC

  GROUP BY S#

  ) AS T1

  WHERE 平均成绩 > T2.平均成绩) as 名次,

  S# as 学生学号,平均成绩

  FROM (SELECT S#,AVG(score) 平均成绩

  FROM SC

  GROUP BY S#

  ) AS T2

  ORDER BY 平均成绩 desc;

  25、查询各科成绩前三名的记录:(不考虑成绩并列情况)

  SELECT t1.S# as 学生ID,t1.C# as 课程ID,Score as 分数

  FROM SC t1

  WHERE score IN (SELECT TOP 3 score

  FROM SC

  WHERE t1.C#= C#

  ORDER BY score DESC

  )

  ORDER BY t1.C#;

  26、查询每门课程被选修的学生数

  select c#,count(S#) from sc group by C#;

  27、查询出只选修了一门课程的全部学生的学号和姓名

  select SC.S#,Student.Sname,count(C#) AS 选课数

  from SC ,Student

  where SC.S#=Student.S# group by SC.S# ,Student.Sname having count(C#)=1;

  28、查询男生、女生人数

  Select count(Ssex) as 男生人数 from Student group by Ssex having Ssex='男';

  Select count(Ssex) as 女生人数 from Student group by Ssex having Ssex='女';

  29、查询姓“张”的学生名单

  SELECT Sname FROM Student WHERE Sname like '张%';

  30、查询同名同性学生名单,并统计同名人数

  select Sname,count(*) from Student group by Sname having count(*)>1;;

  31、1981年出生的学生名单(注:Student表中Sage列的类型是datetime)

  select Sname, CONVERT(char (11),DATEPART(year,Sage)) as age

  from student

  where CONVERT(11),DATEPART(year,Sage))='1981';

  32、查询每门课程的平均成绩,结果按平均成绩升序排列,平均成绩相同时,按课程号降序排列

  Select C#,Avg(score) from SC group by C# order by Avg(score),C# DESC ;

  33、查询平均成绩大于85的所有学生的学号、姓名和平均成绩

  select Sname,SC.S# ,avg(score)

  from Student,SC

  where Student.S#=SC.S# group by SC.S#,Sname having avg(score)>85;

  34、查询课程名称为“数据库”,且分数低于60的`学生姓名和分数

  Select Sname,isnull(score,0)

  from Student,SC,Course

  where SC.S#=Student.S# and SC.C#=Course.C# and Course.Cname='数据库'and score<60;

  35、查询所有学生的选课情况;

  SELECT SC.S#,SC.C#,Sname,Cname

  FROM SC,Student,Course

  where SC.S#=Student.S# and SC.C#=Course.C# ;

  36、查询任何一门课程成绩在70分以上的姓名、课程名称和分数;

  SELECT distinct student.S#,student.Sname,SC.C#,SC.score

  FROM student,Sc

  WHERE SC.score>=70 AND SC.S#=student.S#;

  37、查询不及格的课程,并按课程号从大到小排列

  select c# from sc where scor e<60 order by C# ;

  38、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名;

  select SC.S#,Student.Sname from SC,Student where SC.S#=Student.S# and Score>80 and C#='003';

  39、求选了课程的学生人数

  select count(*) from sc;

  40、查询选修“叶平”老师所授课程的学生中,成绩最高的学生姓名及其成绩

  select Student.Sname,score

  from Student,SC,Course C,Teacher

  where Student.S#=SC.S# and SC.C#=C.C# and C.T#=Teacher.T# and Teacher.Tname='叶平' and SC.score=(select max(score)from SC where C#=C.C# );

  41、查询各个课程及相应的选修人数

  select count(*) from sc group by C#;

  42、查询不同课程成绩相同的学生的学号、课程号、学生成绩

  select distinct A.S#,B.score from SC A ,SC B where A.Score=B.Score and A.C# <>B.C# ;

  43、查询每门功成绩最好的前两名

  SELECT t1.S# as 学生ID,t1.C# as 课程ID,Score as 分数

  FROM SC t1

  WHERE score IN (SELECT TOP 2 score

  FROM SC

  WHERE t1.C#= C#

  ORDER BY score DESC

  )

  ORDER BY t1.C#;

  44、统计每门课程的学生选修人数(超过10人的课程才统计)。要求输出课程号和选修人数,查询结果按人数降序排列,查询结果按人数降序排列,若人数相同,按课程号升序排列

  select C# as 课程号,count(*) as 人数

  from sc

  group by C#

  order by count(*) desc,c#

  45、检索至少选修两门课程的学生学号

  select S#

  from sc

  group by s#

  having count(*) > = 2

  46、查询全部学生都选修的课程的课程号和课程名

  select C#,Cname

  from Course

  where C# in (select c# from sc group by c#)

  47、查询没学过“叶平”老师讲授的任一门课程的学生姓名

  select Sname from Student where S# not in (select S# from Course,Teacher,SC where Course.T#=Teacher.T# and SC.C#=course.C# and Tname='叶平');

  48、查询两门以上不及格课程的同学的学号及其平均成绩

  select S#,avg(isnull(score,0)) from SC where S# in (select S# from SC where score<60 group="" by="" having="">2)group by S#;

  49、检索“004”课程分数小于60,按分数降序排列的同学学号

  select S# from SC where C#='004'and score<60 order by score desc;

  50、删除“002”同学的“001”课程的成绩

  from Sc where S#='001'and C#='001';

  一、SQL语言简介

  1、SQL语言简介

  SQL是结构化查询语言(Structured Query Language),是用于访问和处理数据库的标准的计算机语言。

  SQL语言的功能如下:

  A、SQL面向数据库执行查询

  B、SQL可从数据库取回数据

  C、SQL可在数据库中插入新的记录

  D、SQL可更新数据库中的数据

  E、SQL可从数据库删除记录

  F、SQL可创建新数据库

  G、SQL可在数据库中创建新表

  H、SQL可在数据库中创建存储过程

  I、SQL可在数据库中创建视图

  J、SQL可以设置表、存储过程和视图的权限

  SQL是一门ANSI的标准计算机语言,用来访问和操作数据库系统。SQL语句用于取回和更新数据库中的数据。SQL可与数据库程序协同工作,比如MS Access、DB2、Informix、MS SQL Server、Oracle、MySQL、Sybase以及其他数据库系统。

  每一种数据库有自己版本的SQL语言,但是为了与ANSI标准相兼容,SQL必须以相似的方式共同地来支持一些主要的关键词(比如 SELECT、UPDATE、DELETE、INSERT、WHERE等等)。

  除了SQL标准之外,大部分SQL数据库程序都拥有自己的私有扩展。

  2、SQL语言分类

  SQL语言分为数据定义语言、数据控制语言、数据操作语言、数据查询语言,分别实现对数据库数据操作。

  二、SQL语言基础

  1、数据定义语言(DDL)

  DDL:Data Definition Language

  用于定义和管理数据对象,包括数据库、数据表、函数、视图、索引、触发器等。例如:CREATE、DROP、ALTER等语句。

  create table student

  (

  sid INT,

  sname var20)

  );

  alter table student add age int default 20;

   student;

  drop database student;

  2、数据控制语言(DCL)

  DCL:Data Control Language

  用来管理数据库的语言,包含授权用户访问、拒绝用户访问、撤销授予的权限。例如:GRANT、DENY、REVOKE、COMMIT、ROLLBACK等语句。

  创建用户

  create user ‘wang’@‘localhost’ identified by ‘a1!’;

  权限设置

  grant select on db.student to ‘wang’@‘localhost’;

  撤销权限

  revoke select on db.student from ‘wang’@‘localhost’;

  3、数据操作语言(DML)

  DML:Data Manipulation Language

  用于操作数据库对象中所包含的数据,增、删、改。例如:INSERT、DELETE、UPDATE语句。

  4、数据查询语言(DQL)

  DQL:Data Query Language

  用于查询数据库对象中所包含的数据,能够进行单表查询、连接查询、嵌套查询,以及集合查询等各种复杂程度不同的数据库查询,并将数据返回到客户机中显示。例如:SELECT语句。

  三、常量和变量

  1、常量

  A、字符常量

  字符串常量使用单引号或双引号,数值常量不用加引号。

  如果字符串常量中需要换行、有单引号、双引号 % _

  前面需要加转义字符

   换行

  ’ 一个单引号

  ” 一个双引号

   一个 如果没有转义字符 就认为是一个转义字符

  % 一个% 如果没有转义字符就认为这是一个通配符

  _ 一个_ 如果没有转移字符 就认为是一个通配符

  select ‘hanli’gang001’

  select ‘han ligang001’

  select ‘han ligang001’

  select “han"ligang001”

  select “韩立刚001”

  B、数值常量

  数值常量不用添加引号,

  select 100+100+200

  C、布尔常量

  布尔型常量取值 true 和 false

  在SQL中使用1和0表示

  select true,false

  在表达式中

  select 100>200

  select 100<200

  2、变量

  用户自定义变量使用@开始,使用set给变量赋值。

  set @name=‘孙悟空’;

  select @name;

  select * from student;

   into student values (6,‘孙悟空’,20);

   into student values (8,@name,20);

  set @sid=9,@nid=10

   into student values (@sid,@name,20);

  select @sid+@nid;

  set @sid=@sid+1;

  select @sid;

  set @sname3=(select sname from student where sid=9);

  select @sname3;

  3、系统变量

  系统变量分为全局系统变量和会话系统变量。

  全局系统变量:针对所有默认设置

  会话系统变量:针对当前用户生效,用户登录MySQL会使用全局系统变量,如果会话中更改了变量值,使用更改后的值,不过只针对当前用户生效。

  show variables 显示会话系统变量

  show global variables 显示全局系统变量

  show session variables 显示会话系统变量

  show global variables like ‘sql_select_limit’;使用通配符显示匹配的变量设置

  show session variables like ‘sql_select_limit’;系统变量使用@@标识

  select @@global.sql_select_limit 查看某个全局系统变量设置

  select @@session.sql_select_limit 查看某个会话系统变量设置

  set @@session.sql_select_limit=2 设置会话系统变量

  全局系统变量需要在/etc/my.cnf配置文件中修改。