Question

我有一张城市表，基于邮政编码的州。因此，如果有人搜索芝加哥，由于邮政编码的数量，他们会得到30个芝加哥列表。我想只获得芝加哥的一个列表...但我也想返回zip字段（因为我不需要它）。下面将返回单排“芝加哥，il”，但它也不会通过拉链......它怎么能通过拉链。

SELECT DISTINCT City, State FROM Zips where City like 'chicago' ORDER BY State

拉链表

*Zip | City | State | Lat | Long

Answer 1

SELECT City, State, MIN(Zip) AS ZIP
  FROM Zips
 WHERE City = 'chicago'
 GROUP BY City, State
 ORDER BY State;

或者，也许更具信息性：

SELECT City, State, MIN(Zip) AS Min_ZIP, MAX(Zip) AS Max_ZIP
  FROM Zips
 WHERE City = 'chicago'
 GROUP BY City, State
 ORDER BY State;

是否也可以允许输入搜索采用邮政编码和/或城市？

搜索邮政编码：

SELECT City, State, MIN(Zip) AS Min_ZIP, MAX(Zip) AS Max_ZIP
  FROM Zips
 WHERE Zip = '01234'
 GROUP BY City, State
 ORDER BY State;

搜索zip和city：

SELECT City, State, MIN(Zip) AS Min_ZIP, MAX(Zip) AS Max_ZIP
  FROM Zips
 WHERE City = 'chicago'
   AND Zip = '01234'
 GROUP BY City, State
 ORDER BY State;

搜索zip或城市：

SELECT City, State, MIN(Zip) AS Min_ZIP, MAX(Zip) AS Max_ZIP
  FROM Zips
 WHERE City = 'chicago'
    OR Zip = '01234'
 GROUP BY City, State
 ORDER BY State;

使用单个查询来搜索zip（除非它为null）或城市（除非为null）更为棘手。它通常最终使用问号占位符等 - 并且不能完全跨DBMS移植（而上述查询都可以移植到任何SQL DBMS）。

SELECT City, State, MIN(Zip) AS Min_ZIP, MAX(Zip) AS Max_ZIP
  FROM Zips
 WHERE (? IS NOT NULL AND City = ?)
    OR (? IS NOT NULL AND Zip  = ?)
 GROUP BY City, State
 ORDER BY State;

在这里，如果它有效，你将提供两次城市参数（前两个问号中的每一个一次）和两次zip参数（最后两个问号中的每一个一次）。这进入了讨论哪种编程语言的领域。一些DBMS允许您使用诸如“:n”之类的表示法来编写每个参数一次，以识别不同的参数：

SELECT City, State, MIN(Zip) AS Min_ZIP, MAX(Zip) AS Max_ZIP
  FROM Zips
 WHERE (:1 IS NOT NULL AND City = :1)
    OR (:2 IS NOT NULL AND Zip  = :2)
 GROUP BY City, State
 ORDER BY State;

我不知道MySQL在这个领域提供了什么。

Answer 2

假设Zip代码位于名为Zip的字段中，您可以尝试：

SELECT City, State, MIN(Zip) 
FROM Zips 
WHERE City LIKE 'chicago'
GROUP BY City, State

对于您所描述的内容，您将被迫选择MIN或MAX邮政编码。

Answer 3

如果我知道您不关心您回复的邮政编码，我认为您正在寻找

LIMIT 1

将它放在SQL语句的末尾。

SELECT City, State, Zipcode FROM Zips where City like 'chicago' LIMIT 1;

除非你的城市可能出现在多个州？

Answer 4

假设Zips在Zip上是唯一的，另一种解决方案是：

Select Zip, City, State, Lat, Long
From Zips
Where Zip   =  (
                Select Min(Z1.Zip)
                From Zips As Z1
                Where Z1.City = 'chicago'
                )

任意选择任何名为“芝加哥”的城市的“最低”邮政编码。但是，如果那就足够了，我会感到惊讶。搜索纯粹基于城市名称的邮政编码永远不会在逻辑上足够。至少，您可能希望按州缩小范围，或显示包含所请求城市的所有国家。

如果您想搜索邮政编码或城市，可以这样做：

Select Zip, City, State, Lat, Long
From Zips
Where Zip   =   (
                    Select Min(Z1.Zip)
                    From Zips As Z1
                    Where Z1.City = 'chicago'
                        Or Z1.Zip = '12345'
                    )

sql查询唯一/不同的行

4 个答案: