Question

我不是一个sql master，这句话对我来说没有意义。因此，如果任何人能够为我分解并让我知道究竟是什么，我会非常感激。

声明：

SELECT a.accountid,a.firstname,a.lastname,a.miName,a.legacyAccountid,a.accountType,
SELECT count(invoices.invID) AS InvCount 
FROM invoices 
WHERE invoices.accountid = a.accountid AND invoices.statusID=0 AND invoices.Remaining>0
AND dueDate < DATEADD(Day,1,GETDATE()) AS AccountStatus,
SELECT count(lotOwnership.lotNumb) AS LotCount FROM lotOwnership WHERE lotOwnership.accountid = a.accountid AS Active
FROM a
WHERE a.accountid LIKE % var % OR a.legAccountid LIKE % var % OR a.lastname LIKE % var % AND a.accountType=1 ORDER BY a.lastname, a.firstname

我很想知道的是：

图中的frack是如何合法的？我引用了整个语句，特别是这个嵌套的select：

SELECT count(lotOwnership.lotNumb) AS LotCount FROM lotOwnership WHERE lotOwnership.accountid = a.accountid AS Active

出于某种原因，我无法绕过这个。有人请救救我！我不明白一个选择语句如何有两个AS别名??????????????????????

Answer 1

相关的子查询需要用括号括起来。然后，它是有道理的，因为它们产生标量值，然后用AS别名。

如果OP中的代码运行，那么应用程序必须知道如何在没有添加括号的情况下隔离子查询。

SELECT 
    a.accountid,
    a.firstname,
    a.lastname,
    a.miName,
    a.legacyAccountid,
    a.accountType,
    (SELECT 
        count(invoices.invID) AS InvCount 
        FROM invoices 
        WHERE invoices.accountid = a.accountid 
        AND invoices.statusID=0 
        AND invoices.Remaining>0
        AND dueDate < DATEADD(Day,1,GETDATE())) AS AccountStatus,
    (SELECT 
        count(lotOwnership.lotNumb) AS LotCount 
        FROM lotOwnership 
        WHERE lotOwnership.accountid = a.accountid) AS Active
FROM a
WHERE a.accountid LIKE % var % 
    OR a.legAccountid LIKE % var % 
    OR a.lastname LIKE % var % 
    AND a.accountType=1 
ORDER BY a.lastname, a.firstname

Answer 2

代码缺少子查询周围的括号和字符串周围的引号：

SELECT a.accountid,a.firstname,a.lastname,a.miName,a.legacyAccountid,a.accountType,
(SELECT count(invoices.invID) AS InvCount 
 FROM invoices 
 WHERE invoices.accountid = a.accountid AND invoices.statusID=0 AND invoices.Remaining>0
 AND dueDate < DATEADD(Day,1,GETDATE())
) AS AccountStatus,
(SELECT count(lotOwnership.lotNumb) AS LotCount FROM lotOwnership WHERE lotOwnership.accountid = a.accountid
) AS Active
FROM a
WHERE a.accountid LIKE' % var %' OR a.legAccountid LIKE '% var %' OR a.lastname LIKE '% var %' AND a.accountType=1
ORDER BY a.lastname, a.firstname

我对丑陋的编码风格进行了极少的重新格式化，因此您可以看到更改的位置。知道为什么这些字符丢失了吗？

编辑：

考虑select的前两行（现在格式更好）：

SELECT a.accountid, a.firstname, a.lastname, a.miName, a.legacyAccountid, a.accountType,
       (SELECT count(invoices.invID) AS InvCount 
        FROM invoices 
        WHERE invoices.accountid = a.accountid AND
              invoices.statusID = 0 AND
              invoices.Remaining > 0 AND
              dueDate < DATEADD(Day,1,GETDATE())
      ) AS AccountStatus,

子查询定义为返回名为InvCount的列。如果您单独运行它，它将有一个名为InvCount的列。

在此上下文中，它是一个标量子查询。也就是说，返回（最多）一行和一个值的子查询。在该上下文中，返回的值被视为表达式的结果。因此，子查询中名为InvCount的列在外部查询中名为AccountStatus。您可以将其视为：

select ((select  . . . ) as InvCount) as AccountStatus

当然，这种语法不合法，但它从概念上捕捉了会发生什么。第一个别名被忽略了。

选择带有/ TWO AS别名的语句？

2 个答案: