想要成為合格的Java後端開發(fā)者，資料庫知識(shí)必不可少，對(duì)資料庫的掌握熟悉度的考察也是對(duì)這個(gè)人是否有紮實(shí)基本功的考察。

（更多相關(guān)面試題推薦：java面試題目及答案）

特別對(duì)於初級(jí)開發(fā)者，面試可能不會(huì)去問框架相關(guān)知識(shí)，但絕對(duì)不會(huì)不去考察資料庫知識(shí)，這裡收集一些常見類型的SQL語句，無論對(duì)於平常開發(fā)還是準(zhǔn)備面試，都會(huì)有助益。

基本表架構(gòu)：

 student(sno,sname,sage,ssex)學(xué)生表        
 course(cno,cname,tno) 課程表        
 sc(sno,cno,score) 成績(jī)表
 teacher(tno,tname) 教師表

101，查詢課程1的成績(jī)比課程2的成績(jī)高的所有學(xué)生的學(xué)號(hào)

select a.sno from
(select sno,score from sc where cno=1) a,
(select sno,score from sc where cno=2) b
where a.score>b.score and a.sno=b.sno

102，查詢平均成績(jī)大於60分的同學(xué)的學(xué)號(hào)和平均成績(jī)

select a.sno as "學(xué)號(hào)", avg(a.score) as "平均成績(jī)" 
from
(select sno,score from sc) a 
group by sno having avg(a.score)>60

103，查詢所有同學(xué)的學(xué)號(hào)、姓名、選課數(shù)、總成績(jī)

select a.sno as 學(xué)號(hào), b.sname as 姓名,
count(a.cno) as 選課數(shù), sum(a.score) as 總成績(jī)
from sc a, student b
where a.sno = b.sno
group by a.sno, b.sname

或：

selectstudent.sno as 學(xué)號(hào), student.sname as 姓名,
 count(sc.cno) as 選課數(shù), sum(score) as 總成績(jī)
from student left Outer join sc on student.sno = sc.sno
group by student.sno, sname

104，查詢姓「張」的老師的個(gè)數(shù)

selectcount(distinct(tname)) from teacher where tname like '張%‘

或：

select tname as "姓名", count(distinct(tname)) as "人數(shù)" 
from teacher 
where tname like'張%'
group by tname

105，查詢沒學(xué)過「張三」老師課的同學(xué)的學(xué)號(hào)、姓名

select student.sno,student.sname from student
where sno not in (select distinct(sc.sno) from sc,course,teacher
where sc.cno=course.cno and teacher.tno=course.tno and teacher.tname='張三')

（推薦學(xué)習(xí)：java課程）

106，查詢同時(shí)學(xué)過課程1和課程2的同學(xué)的學(xué)號(hào)、姓名

select sno, sname from student
where sno in (select sno from sc where sc.cno = 1)
and sno in (select sno from sc where sc.cno = 2)

或：

selectc.sno, c.sname from
(select sno from sc where sc.cno = 1) a,
(select sno from sc where sc.cno = 2) b,
student c
where a.sno = b.sno and a.sno = c.sno

或：

select student.sno,student.sname from student,sc where student.sno=sc.sno and sc.cno=1
and exists( select * from sc as sc_2 where sc_2.sno=sc.sno and sc_2.cno=2)

107，查詢學(xué)過「李四」老師所教所有課程的所有同學(xué)的學(xué)號(hào)、姓名

select a.sno, a.sname from student a, sc b
where a.sno = b.sno and b.cno in
(select c.cno from course c, teacher d where c.tno = d.tno and d.tname = '李四')

或：

select a.sno, a.sname from student a, sc b,
(select c.cno from course c, teacher d where c.tno = d.tno and d.tname = '李四') e
where a.sno = b.sno and b.cno = e.cno

108，查詢課程編號(hào)1的成績(jī)比課程編號(hào)2的成績(jī)高的所有同學(xué)的學(xué)號(hào)、姓名

select a.sno, a.sname from student a,
(select sno, score from sc where cno = 1) b,
(select sno, score from sc where cno = 2) c
where b.score > c.score and b.sno = c.sno and a.sno = b.sno

109，查詢所有課程成績(jī)小於60分的同學(xué)的學(xué)號(hào)、姓名

select sno,sname from student
where sno not in (select distinct sno from sc where score > 60)

110，查詢至少有一門課程與學(xué)號(hào)為1的同學(xué)所學(xué)課程相同的同學(xué)的學(xué)號(hào)和姓名

select distinct a.sno, a.sname
from student a, sc b
where a.sno <> 1 and a.sno=b.sno and
b.cno in (select cno from sc where sno = 1)

或：

select s.sno,s.sname 
from student s,
(select sc.sno 
from sc
where sc.cno in (select sc1.cno from sc sc1 where sc1.sno=1)and sc.sno<>1
group by sc.sno)r1
where r1.sno=s.sno

相關(guān)推薦：java入門教學(xué)

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