SQL Server：是否可以從聚合函數中選擇別名列？

Question

所以我有一個從執行聚合函數這些列： 表

SELECT MachineName,

       (100*((1)
       -((
       sum(CASE p1.CounterName
             WHEN 'Available Bytes' THEN
               p2.CounterValue
             ELSE
               0
           END)
       /NULLIF(
       (sum(CASE p1.CounterName
              WHEN 'Available Bytes' THEN
                p2.CounterValue
              ELSE
                0
            END)
        +
        sum(CASE p1.CounterName
              WHEN 'Committed Bytes' THEN
                p2.CounterValue
              ELSE
                0
            END)
        +
        sum(CASE p1.CounterName
              WHEN 'Modified Page List Bytes' THEN
                p2.CounterValue
              ELSE
                0
            END)),0) ))))  As Memory

我只希望選擇需要> 75的“內存”，但是我對SQL和聚合函數不夠熟悉，因此我不確定是否可行。

Answer 1

您可以嘗試使用如下子查詢-

select * from 
(
SELECT MachineName,

       (100*((1)
       -((
       sum(CASE p1.CounterName
             WHEN 'Available Bytes' THEN
               p2.CounterValue
             ELSE
               0
           END)
       /NULLIF(
       (sum(CASE p1.CounterName
              WHEN 'Available Bytes' THEN
                p2.CounterValue
              ELSE
                0
            END)
        +
        sum(CASE p1.CounterName
              WHEN 'Committed Bytes' THEN
                p2.CounterValue
              ELSE
                0
            END)
        +
        sum(CASE p1.CounterName
              WHEN 'Modified Page List Bytes' THEN
                p2.CounterValue
              ELSE
                0
            END)),0) ))))  As Memory
)A where memory>75