1、用一條SQL語句查詢出每門課都大於80分的學生姓名

 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(‘張三‘,‘語文
 
‘,81),(‘張三‘,‘數學‘,75),(‘李四‘,‘語文‘,76),(‘李四‘,‘數學‘,90),(‘王五‘,‘語文‘,81),(‘王五‘,‘數學‘,100),(‘王五‘,‘英語‘,90)
 7 
 8 select * from chengji1
 9 --distinct 用於返回唯一不同的值--
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關鍵字無法與合計函數一起使用--
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 

2、刪除除了自動編號不同, 其他都相同的學生冗余信息

 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‘,‘張三‘,‘0001‘,‘數學‘,69),(‘2005002‘,‘李四‘,‘0001‘,‘數學‘,89),(‘2005001‘,‘張三‘,‘0001‘,‘數學‘,69)
10 select * from stutable1
11 delete stutable1 where id not in (select  MIN(id) from stutable1 group by stunumber,name,kcnumber,kecheng,fenshu)

3、面試題：怎麽把這樣一個表兒

查成這樣一個結果

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

4、說明：拷貝表( 拷貝數據, 源表名：a 目標表名：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

SQL 基礎練習