Question

客户表

number = 666，ContactId = 1a1b ..

联系表

Id = 1a1b ..，Name = Bob smith

地址表

地址= 350 king road，AddressType = officle，Order = 1，ContactId = 1a1b 地址= 123皇后街，AddressType = home，Order = 2，ContactId = 1a1b

SQL查询：

SELECT TOP (100)  
    dbo.Customer.Number, dbo.Contact.Name, 
    dbo.Address.StreetAddress, dbo.Address.Order 
FROM
    dbo.Customer 
LEFT JOIN
    dbo.Contact ON dbo.Customer.ContactId = dbo.Contact.Id 
LEFT JOIN
    dbo.Address ON dbo.Contact.Id = dbo.Address.ContactId
WHERE
    Contact.Name LIKE '%o%' OR Address.StreetAddress LIKE '%o%'

返回以下结果：

666 | Bob Smith | 350 king road | 1
666 | Bob Smith | 123 queen street | 2

问题：

我想获得第一个可用地址（350王道/序列1）而不是两者（即使搜索字符串与两个地址匹配）

当匹配仅在第二个地址上时（比如在我的示例中执行类似％q％而不是类似％o％）我想返回此特定地址而不是其他地址

是否可以在SQL中执行此操作？顺便说一句，我的目标也是尽可能快地得到结果，还有其他方法可以在“一对多”连接表中进行这种搜索吗？

我只需要一些东西......谢谢！

Answer 1

您需要考虑Contact.Name LIKE＆＃39;％o％＆＃39;可能会返回多个唯一名称

否则左边的值也可以使用连接

select top 100 * 
from
(
SELECT dbo.Customer.Number, 
       dbo.Contact.Name, 
       dbo.Address.StreetAddress, 
       row_number() over (partition by dbo.Customer.Number order dbo.Address.Order) as rn
  FROM dbo.Customer 
  JOIN dbo.Contact 
        ON dbo.Contact.Id        = dbo.Customer.ContactId          
  JOIN dbo.Address 
        ON dbo.Address.ContactId = dbo.Customer.ContactId -- = dbo.Contact.Id   
 where Contact.Name LIKE '%o%' 
    or Address.StreetAddress LIKE '%o%'
) tt 
where tt.rn = 1
order by tt.Customer.Number

我认为你可以通过dbo.Customer.Number进行分区，但你可能需要添加dbo.Contact.Name和dbo.Address.StreetAddress

如果你想使用左边那么你需要
（Contact.Name LIKE＆＃39;％o％＆＃39;或Contact.Name为空）
和地址需要加入dbo.Customer.ContactId
获得空连接

Answer 2

如果您始终需要基于地址表中排序顺序的单个记录，只需按该字段对结果进行排序，并将结果限制为TOP (1)而不是TOP（100）。

SELECT TOP (1)  
    dbo.Customer.Number, dbo.Contact.Name, 
    dbo.Address.StreetAddress, dbo.Address.Order 
FROM
    dbo.Customer 
LEFT JOIN
    dbo.Contact ON dbo.Customer.ContactId = dbo.Contact.Id 
LEFT JOIN
    dbo.Address ON dbo.Contact.Id = dbo.Address.ContactId
WHERE
    Contact.Name LIKE '%o%' OR Address.StreetAddress LIKE '%o%'
ORDER BY dbo.Address.Order ASC

Answer 3

如果您计划检索多个客户，但只有每个客户的主要地址，您可以在子查询中使用row_number（），并且只返回每个分区（客户）的第1行，如下所示：

SELECT dbo.Customer.Number,
       dbo.Contact.Name,
       dbo.Address.StreetAddress,
   dbo.Address.Order
  FROM (SELECT TOP (100) Row_number()
                           OVER (
                             partition BY dbo.Customer.Number, dbo.Contact.Name
                             ORDER BY dbo.Address.Order) AS seq,
                         dbo.Customer.Number,
                         dbo.Contact.Name,
                         dbo.Address.StreetAddress,
                         dbo.Address.Order
          FROM dbo.Customer
               LEFT JOIN dbo.Contact
                      ON dbo.Customer.ContactId = dbo.Contact.Id
               LEFT JOIN dbo.Address
                      ON dbo.Contact.Id = dbo.Address.ContactId
     WHERE Contact.Name LIKE '%o%'
        OR Address.StreetAddress LIKE '%o%') t
 WHERE t.seq = 1

当连接在多个元素上时的Where子句

3 个答案: