SQL 基础练习

Posted 2020-10-28 冬月二四

name	kecheng	fenshu
张三	语文	81
张三	数学	75
李四	语文	76
李四	数学	90
王五	语文	81
王五	数学	100
王五	英语	90

1、用一条SQL语句查询出每门课都大于80分的学生姓名

 1 create table chengji1(
 2 name  varchar(50) not null,
 3 kecheng varchar(50) not null,
 4 fenshu int not null
 5 )
 6 insert chengji1(name,kecheng,fenshu)values(\'张三\',\'语文\',81),(\'张三\',\'数学\',75),(\'李四\',\'语文\',76),(\'李四\',\'数学\',90),(\'王五\',\'语文\',81),(\'王五\',\'数学\',100),(\'王五\',\'英语\',90)
 7 
 8 select * from chengji1
 9 --distinct 用于返回唯一不同的值--
10 select distinct name from chengji1 where name not in (select distinct name from chengji1 where fenshu <= 80 )
11 --增加having字句的原因是，where关键字无法与合计函数一起使用--
12 select name from chengji1 group by name having min(fenshu)> 80
13 ----
14 select name from chengji1 group by name having COUNT(kecheng) >= 3 and MIN(fenshu) >= 80 

View Code

 

2、删除除了自动编号不同, 其他都相同的学生冗余信息

 1 create table stutable1(
 2 id int primary key IDENTITY(1,1) not null,
 3 stunumber varchar(20) not null,
 4 name varchar(20) not null,
 5 kcnumber varchar(20) not null,
 6 kecheng varchar(20) not null,
 7 fenshu int not null
 8 )
 9 insert stutable1(stunumber,name,kcnumber,kecheng,fenshu) values(\'2005001\',\'张三\',\'0001\',\'数学\',69),(\'2005002\',\'李四\',\'0001\',\'数学\',89),(\'2005001\',\'张三\',\'0001\',\'数学\',69)
10 select * from stutable1
11 delete stutable1 where id not in (select  MIN(id) from stutable1 group by stunumber,name,kcnumber,kecheng,fenshu)

答案

3、面试题：怎么把这样一个表儿

查成这样一个结果

create table yma(
year int not null,
month int not null,
amount decimal(18,1) not null
)
insert yma values(1991,1,1.1),(1991,2,1.2),(1991,3,1.3),(1991,4,1.4),(1992,1,2.1),(1992,2,2.2),(1992,3,2.3),(1992,4,2.4)
select * from yma
delete from yma

select year,
(select amount from yma m where month =1 and m.year= yma.year) as m1,
(select amount from yma m where month =2 and m.year= yma.year) as m2,
(select amount from yma m where month =3 and m.year= yma.year) as m3,
(select amount from yma m where month =4 and m.year= yma.year) as m4
from yma group by year

答案

4、说明：拷贝表( 拷贝数据, 源表名：a 目标表名：b)

create table yma1(
year int not null,
month int not null,
amount decimal(18,1) not null
)
insert into yma1(year,month,amount)select year,month,amount from yma
select * from yma1

答案

 5、通过 SQL，您如何按字母顺序选取 Persons 表中 LastName 介于 Adams 和 Carter 的所有记录？

SELECT * FROM Persons WHERE LastName BETWEEN \'Adams\' AND \'Carter\'

6、通过 SQL，您如何从 "Persons" 表中选取 "FirstName" 列的值以 "a" 开头的所有记录？

SELECT * FROM Persons WHERE FirstName LIKE \'a%\'