Question

我有一个现有的SQL查询，我需要为它添加一个连接，这样只有当另一个表中的列的值与join指定的相同时，才会返回此查询的结果。我过去做过加入，但他们总是在简单的查询上。我只是不确定在哪里插入连接，我尝试的一切都有语法问题。用英语我想：

现有的查询...加入另一个表，其中ANOTHERTABLE.COLUMNNAME =“SOMEVALUE”

查询是：

    ; WITH cte_DateFormat AS (SELECT        ServerName, CONVERT(DATE, Date, 103) AS Date, [Capacity(GB)], [Free Space (GB)], Region
                                                           FROM            [Some_Table]), cte_Rank AS
    (SELECT        ROW_NUMBER() OVER (PARTITION BY ServerName, CAST(YEAR(Date) AS VARCHAR(4)) + CAST(MONTH(Date) AS VARCHAR(2))
      ORDER BY Date DESC) AS ID, Region, ServerName, Date, [Capacity (GB)], [Free Space (GB)]
FROM            cte_DateFormat)
    SELECT        Region, ServerName, Date, [Capacity (GB)], [Free Space (GB)]
     FROM            cte_Rank
     WHERE        ID = 1
     ORDER BY Date DESC, Region DESC

Answer 1

听起来你不想加入，你想要求另一个表中存在一个值。所以使用EXISTS：

; WITH cte_DateFormat AS (...) , cte_Rank AS (...)
SELECT Region, ServerName, Date, [Capacity (GB)], [Free Space (GB)]
FROM cte_Rank
WHERE ID = 1
AND EXISTS
(
  select * 
  from anothertable 
  where anothertable.servername = cte_Rank.ServerName 
  and ... -- some other criteria if needed
)
ORDER BY Date DESC, Region DESC

将连接添加到复杂的SQL查询

1 个答案: