|
1
|
**SQL多表连查**
|
|
1
2
3
4
5
6
7
8
|
--查询员工和部门信息
select
*
from
emp e,dept d
where
e.deptno=d.deptno
--查询员工姓名，部门名称
select
e.ename,d.dname
from
emp e,dept d
where
e.deptno = d.deptno
--查询所有员工姓名，部门名称
select
e.*, d.dname
from
emp e,dept d
where
e.deptno=d.deptno
--查询工资大于3000的员工姓名，工资和部门名称
select
e.ename,e.sal,d.dname
from
emp e,dept d
where
e.deptno=d.deptno
and
e.sal>=3000
|
|
1
2
3
4
|
--非等值查询
--查询公司工资等级
select
*
from
emp e,salgrands
where
e.sal<=s.hisal
and
e.sal>s.losal
select
*
from
salagrade
|
|
1
2
3
4
5
|
--外链接
--左外连接
select
*
from
emp e,dept d
where
e.deptno=d.deptno(+)
--右外连接
select
*
from
emp e,dept d
where
e.deptno(+)=d.deptno
|
|
1
2
3
4
5
6
|
--自连接
--查询员工姓名和经理姓名
select
e1.ename ,e2.ename
from
emp e1,emp e2
where
e1.mgr=e2.deptno
--查询员工姓名、经理姓名和其他经理姓名
select
e1.ename,e2.ename,e3.ename
from
emp e1,emp e2, emp e3
where
e1.mgr=e2.empno
and
e2.empno=e3.empno
|
|
1
|
**以上为92版仅在面试出现**
|
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
|
--SQL99 表连接
--交叉连接 cross join
select
*
from
emp e
cross
join
dept d
--自然连接 natural join
select
*
from
emp natural
join
dept
--using
select
e.ename,deptno
from
emp e
join
dept d using(deptno)
--on 自定义连接
select
*
from
emp e
join
dept d
on
e.deptno=d.deptno
select
*
from
emp e1
join
emp e2
on
e1.mgr=e2.empno
--查询员工的姓名、经理及其经理的名字
select
e1.ename,e2.ename,e3.ename
from
emp e1
join
emp e2
on
e1.mgr=e2.empno
join
emp e3
on
e2.mgr=e3.empno
--SQL99 inner join 两边都合法的数据
select
*
from
emp e
inner
join
dept d
on
e.deptno=d.deptno
--left join 以左表为主
select
*
from
emp e
left
join
dept d
on
e.deptno=d.deptno
--right join 以右表为主
select
*
from
emp e
right
join
dept d
on
e.deptno=d.deptno
--full join 全连 取两个表的所有数据
select
*
from
emp e
full
join
dept d
on
e.deptno=d.deptno
----查询员工的姓名、经理及其经理的名字和部门名字
select
e1.ename, d.dname, e2.ename, d2.dname
from
emp e1
left
join
dept d
on
e1.deptno = d.deptno
left
join
emp e2
on
e2.mgr = e2.empno
left
join
dept d2
on
d2.deptno = d2.deptno
|
|
1
|
**子查询**
|
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
|
--比CLARK工资高的人
select
SAL
from
emp
where
ename=
'CLARK'
select
*
from
emp
where
sal>(
select
SAL
from
emp
where
ename=
'CLARK'
)
--查询工资高于平均工资的雇员姓名和工资
select
avg
(sal)
from
emp
select
ename,sal
from
emp
where
sal>(
select
avg
(sal)
from
emp )
--查询同SCOTT同部门的且工资比他低的员工的名字和工资
select
deptno
from
emp
where
ename=
'SCOTT'
select
sal
from
emp
where
ename=
'SCOTT'
select
ename, sal
from
emp
where
deptno = (
select
deptno
from
emp
where
ename =
'SCOTT'
)
and
sal < (
select
sal
from
emp
where
ename =
'SCOTT'
)
--查询和'SMITH','SCOTT','CLARK'同一个部门的员工姓名
select
distinct
deptno
from
emp
where
ename
in
(
'SMITH'
,
'SCOTT'
,
'CLARK'
)
select
*
from
emp
where
deptno
in
(
select
distinct
deptno
from
emp
where
ename
in
(
'SMITH'
,
'SCOTT'
,
'CLARK'
))
--查询和'SMITH', 'SCOTT', 'CLARK'同一个部门并不包含他们三个的员工姓名
and
ename
not
in
(
'SMITH'
,
'SCOTT'
,
'CLARK'
)
--查询工资最高的员工名字和工资
select
ename,sal
from
emp
where
sal=(
select
max
(sal)
from
emp )
--查询职务和'SCOTT'相同但是比'SCOTT'雇佣时间早的雇员信息
select
*
from
emp
where
job = (
select
job
from
emp
where
ename =
'SCOTT'
)
and
hiredate < (
select
hiredate
from
emp
where
ename =
'SCOTT'
)
--查询工资比'SCOTT'高或者雇佣时间比'SCOTT'早的雇员编号和姓名
select
empno,ename
from
emp
where
job = (
select
job
from
emp
where
ename =
'SCOTT'
)
and
hiredate < (
select
hiredate
from
emp
where
ename =
'SCOTT'
)
|
|
1
|
**多行子查询**
|
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
|
--查询工资低于任何一个“CLERK”的工资的雇员信息
select
*
from
emp
where
sal
all
(
select
sal
from
emp
where
job =
'SALESMAN'
)
--查询部门20中职务同部门10的雇员一样的雇员信息。
select
*
from
emp
where
job
in
(
select
job
from
emp
where
deptno=10)
and
deptno=20
--查询在雇员中有哪些人是经理人
select
*
from
emp
where
empno
in
(
select
distinct
mgr
from
emp
where
mgr
is
not
null
or
mgr !=
''
)
--找出部门编号为20的所有员工中收入最高的职员
select
ename
from
emp
where
sal = (
select
max
(sal)
from
emp
where
deptno = 20)
and
deptno = 20
</
any
(
select
>
|