sql语句中where与having的区别

1.创建名称为bumen、yuangong、gognzi的表。

create table bumen

(
bumen_id int primary key,
bumen_mch nvarchar(100) not null

)

create table yuangong

(
yuangong_id int primary key,
yuangong_name nvarchar(100) not null,
yuangong_gz int,
bumen_id int

)

create table gongzi

(
gongzi_id int primary key,
gongzi_hi int,
gongzi_lw int

)

2.向表中添加数据

insert into bumen values(10,'研发');

insert into bumen values(20,'测试');
insert into bumen values(30,'人力');

select * from bumen

insert into yuangong values(1,'张三',5000,10);

insert into yuangong values(2,'李四',10000,20);

insert into yuangong values(3,'王五',15000,10);
delete from yuangong where yuangong_id=3;

select * from yuangong

insert into gongzi values(1,5000,1500);

insert into gongzi values(2,10000,5001);

insert into gongzi values(3,15000,10001);

select * from gongzi

3.语句的顺序也是不可以改变的。

select * 
--"B".bumen_mch "部门名称",AVG("Y".yuangong_gz) "部门平均工资"
from bumen "B"
join yuangong "Y"
on "B".bumen_id="Y".bumen_id
join gongzi "G"
on "Y".yuangong_gz<="G".gongzi_hi and "Y".yuangong_gz>="G".gongzi_lw

执行结果：

bumen_id	bumen_mch	yuangong_id	yuangong_name	yuangong_gz	bumen_id	gongzi_id	gongzi_hi	gongzi_lw
10	研发	1	张三	5000	10	1	5000	1500
20	测试	2	李四	10000	20	2	10000	5001
10	研发	3	王五	15000	10	3	15000	10001

select * 
--"B".bumen_mch "部门名称",AVG("Y".yuangong_gz) "部门平均工资"
from bumen "B"
join yuangong "Y"
on "B".bumen_id="Y".bumen_id
join gongzi "G"
on "Y".yuangong_gz<="G".gongzi_hi and "Y".yuangong_gz>="G".gongzi_lw
where "Y".yuangong_gz>5000                            --对聚合表的详细内容进行筛选。

执行结果：

bumen_id	bumen_mch	yuangong_id	yuangong_name	yuangong_gz	bumen_id	gongzi_id	gongzi_hi	gongzi_lw
20	测试	2	李四	10000	20	2	10000	5001
10	研发	3	王五	15000	10	3	15000	10001

select "B".bumen_mch "部门名称",AVG("Y".yuangong_gz) "部门平均工资"
from bumen "B"
join yuangong "Y"
on "B".bumen_id="Y".bumen_id
join gongzi "G"
on "Y".yuangong_gz<="G".gongzi_hi and "Y".yuangong_gz>="G".gongzi_lw
where "Y".yuangong_gz>5000                
group by "B".bumen_mch                           --对聚合表进行分组

部门名称	部门平均工资
测试	10000
研发	15000

select "B".bumen_mch "部门名称",AVG("Y".yuangong_gz) "部门平均工资"
from bumen "B"
join yuangong "Y"
on "B".bumen_id="Y".bumen_id
join gongzi "G"
on "Y".yuangong_gz<="G".gongzi_hi and "Y".yuangong_gz>="G".gongzi_lw
where "Y".yuangong_gz>5000                   
group by "B".bumen_mch
having AVG("Y".yuangong_gz)>10000     --对分组表的内容进行筛选。

执行结果：

部门名称	部门平均工资
研发	15000