如何正确表达内部连接

Question

我正在尝试学习联接并已在此处 (SOFlow) 和其他几个地方进行了大量阅读，当然还复制了代码并进行了尝试。

所以我编写了适合我的代码 table:

SELECT
    a.FIRSTNAME, a.LASTNAME, 
    b.[LINE1], b.[LINE2], b.[LINE3], b.[SUBURB], 
    b.[STATE], b.[POSTCODE], 
    p.[PRIVATE], p.[BUSINESS], p.[MOBILE]
FROM
    (SELECT 
         a.UNIQID, a.FIRSTNAME, a.LASTNAME 
     FROM [PTPARTY]) a
INNER JOIN
    (SELECT 
         [LINE1], [LINE2], [LINE3], [SUBURB], [STATE], [POSTCODE], PARTYID 
     FROM 
         [PTAddresses]
     WHERE 
         ADDRESS_TYPE = 'Mailing') b ON a.Uniqid = b.Partyid
INNER JOIN
    (SELECT 
         [Uniqid], [PRIVATE], [BUSINESS], [MOBILE]
     FROM [PTPhone]) P ON a.Uniqid = P.Uniqid
WHERE
    a.UNIQID = 4

但我得到：

Msg 4104, Level 16, State 1, Line 3
The multi-part identifier "a.UNIQID" could not be bound.

Msg 4104, Level 16, State 1, Line 3
The multi-part identifier "a.FIRSTNAME" could not be bound.

Msg 4104, Level 16, State 1, Line 3
The multi-part identifier "a.LASTNAME" could not be bound.

这段代码执行完美的地方

SELECT
    a.FIRSTNAME, a.LASTNAME, 
    b.[LINE1], b.[LINE2], b.[LINE3], b.[SUBURB], b.[STATE], b.[POSTCODE],
    p.[PRIVATE], p.[BUSINESS], p.[MOBILE]
FROM
    (SELECT 
         PTPARTY.UNIQID, PTPARTY.FIRSTNAME, PTPARTY.LASTNAME 
     FROM [PTPARTY]) a
INNER JOIN
    (SELECT 
         [LINE1], [LINE2], [LINE3], [SUBURB], [STATE], [POSTCODE], PARTYID 
     FROM 
         [PTAddresses]
     WHERE
         ADDRESS_TYPE = 'Mailing') b ON a.Uniqid = b.Partyid
INNER JOIN
    (SELECT 
         [Uniqid], [PRIVATE], [BUSINESS], [MOBILE]
     FROM [PTPhone]) P ON a.Uniqid = P.Uniqid
WHERE
    a.UNIQID = 4

我 99% 确定无效的代码是从这里复制的，并进行了更改以适合我的 table 当然。

只是想知道我是否做错了什么。

嗯，我确定我做错了什么，但想知道是什么。

向大家致以诚挚的问候，继续努力

Answer 1

您正在限定子查询中的列，但没有相应的 table 别名：

Select p.FIRSTNAME, p.LASTNAME, a.[LINE1],
       a.[LINE2], a.[LINE3], a.[SUBURB], a.[STATE], a.[POSTCODE],
       ph.[PRIVATE], ph.[BUSINESS], ph.[MOBILE]
 from PTPARTY p inner join
      PTAddresses a
      on p.Uniqid = a.Partyid inner join
      PTPhone ph
      on p.Uniqid = Ph.Uniqid
where a.ADDRESS_TYPE = 'Mailing' and p.UNIQID = 4;

这个真的简单多了。请注意，我将 table 别名替换为含义别名。但是，您不需要子查询：

Answer 2

检查此代码。这会起作用。该错误是由于第一个子查询引起的，因为在第一个子查询中您没有为 table 添加别名，而是使用了 alias.column 名称。所以将其更改为以下内容：

Select a.FIRSTNAME,a.LASTNAME, b.[LINE1],b.[LINE2],b.[LINE3],b.[SUBURB],b.[STATE],b.[POSTCODE],p.[PRIVATE],p.[BUSINESS],p.[MOBILE]
 from
(SELECT UNIQID,FIRSTNAME,LASTNAME FROM [PTPARTY]) a
inner join
(SELECT [LINE1],[LINE2],[LINE3],[SUBURB],[STATE],[POSTCODE],PARTYID FROM [PTAddresses]
  where ADDRESS_TYPE = 'Mailing') b on a.Uniqid = b.Partyid
inner join
(SELECT [Uniqid],[PRIVATE],[BUSINESS],[MOBILE]FROM [PTPhone]) P on a.Uniqid = P.Uniqid
where a.UNIQID = 4

Answer 3

要帮助非常具体：

考虑这部分查询：

FROM
    (SELECT 
         a.UNIQID, a.FIRSTNAME, a.LASTNAME 
     FROM [PTPARTY]) a

当您从子查询中删除括号时，您会得到：

 SELECT 
     a.UNIQID, a.FIRSTNAME, a.LASTNAME 
 FROM [PTPARTY]

项目a.UNIQUID的格式为table别名。列名。但是，括号内，您没有为 [PTPARTY] 指定 table 别名。因此，a.UNIQUID 无效。

因为只有 1 个 table，别名或 table 引用是不必要的。为了清楚起见，我将从这里开始添加 optional "AS"。只有 1 table，您可以仅使用列名来执行此操作：

FROM
    (SELECT 
         UNIQID, FIRSTNAME, LASTNAME 
     FROM [PTPARTY]) AS a

当然，您经常加入 tables 并希望使用别名，因此您可以在括号内这样做：

FROM
    (SELECT 
         z.UNIQID, z.FIRSTNAME, z.LASTNAME 
     FROM [PTPARTY] AS z) AS a

在这种情况下，table 别名 "z" 不在括号外 available/valid。出于这个原因，即使这可能不是最佳实践，您甚至可以重复使用相同的别名。不过，这可能会变得令人困惑。

FROM
    (SELECT 
         a.UNIQID, a.FIRSTNAME, a.LASTNAME 
     FROM [PTPARTY] AS a) AS a

如何正确表达内部连接

How to correctly word an inner join

sql

tsql

sql-server-2008-r2