SQL Server联合查询
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JOIN: 如果表中有至少一个匹配,则返回行
LEFT JOIN: 即使右表中没有匹配,也从左表返回所有的行
RIGHT JOIN: 即使左表中没有匹配,也从右表返回所有的行
FULL JOIN: 只要其中一个表中存在匹配,就返回行
一、inner join
select city.name as 城市, area.name as 地区 from area
inner join city
on city.code = area.cityid
或者
select c.name,a.name from area as a
inner join city as c
on c.code=a.cityid
二、left join
select city.name as 城市,area.name as 地区 from area
left join city
on city.code = area.cityid
或者
select c.name as 城市,a.name as 地区 from area as a
left join city as c
on c.code = a.cityid
三、right join
select city.name as 城市,area.name as 地区 from area
right join city
on city.code = area.cityid
或者
select c.name as 城市,a.name as 地区 from area as a
right join city as c
on c.code = a.cityid
四、full join
select city.name,area.name from area
full join city
on city.code = area.cityid
--或者
select c.name,a.name from area as a
full join city as c
on c.code = a.cityid
表结构
City表
CREATE TABLE [dbo].[city]( [id] [int] NOT NULL, [code] [nvarchar](6) COLLATE Chinese_PRC_CI_AS NULL, [name] [nvarchar](50) COLLATE Chinese_PRC_CI_AS NULL, [provinceId] [nvarchar](6) COLLATE Chinese_PRC_CI_AS NULL) ON [PRIMARY]
Area表
CREATE TABLE [dbo].[area]([id] [int] NOT NULL,[code] [nvarchar](50) COLLATE Chinese_PRC_CI_AS NULL,[name] [nvarchar](60) COLLATE Chinese_PRC_CI_AS NULL,[cityId] [nvarchar](6) COLLATE Chinese_PRC_CI_AS NULL) ON [PRIMARY]
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