SQL与给定的名称只选择第一

Question

房屋

id OwnerId street 
----------------------- 
1 owner1  street1 
2 owner2  street1 
3 owner3  street2 
4 owner4  street2 
5 owner5  street3 

正如你可以看到有可能是在同一条街上更多的业主

我还有一个表，其中我想从Houses表中插入业主，但只有一个来自每个街道

结果查询：

表StreetRepresentant

ownerId street 
------------------ 
owner1  street1 
owner3  street2 
owner5  street3 

（ownerId是表中的PK，如果它很重要。 OwnerId在表Houses）的唯一

查询应该是这样的：

INSERT INTO StreetRepresentant (ownerId , street) 
SELECT ownerId , street 
FROM Houses 
--what should be here to get only 1 owner for each street? ... 

Answer 1

可以组由街道，然后使用MIN()函数返回最低（按你的例子​​） ownerId为每条街道。

SELECT MIN(ownerId) , street 
FROM Houses 
GROUP BY street 

Answer 2

INSERT INTO StreetRepresentant (ownerId , street) 
SELECT ownerId , street 
FROM Houses h 
GROUP BY h.street, h.ownerId 

Answer 3

看一看像

SELECT Street, 
     MIN(ID) FirstAvailableID 
FROM Houses 
GROUP BY Street 

Answer 4

使用DISTINCT关键字的同时选择行，希望它会工作。