保留变量以在SQL Server中的Having子句中使用

Question

SELECT 
    Monitor_Summary.Company_id AS CompanyId, 
    Monitor_Summary.Company_Name,
    COUNT(1) AS Total,
    (SELECT COUNT(1) 
     FROM MONITOR  
     WHERE ISNULL(MONITOR.IPWarning_ind, 0) = 1
       AND MONITOR.Company_id = Monitor_Summary.Company_ID
       AND MONITOR.Status_ind NOT IN (1,0)) AS NewWarnings      
FROM 
    Monitor_Summary
GROUP BY 
    Monitor_Summary.Company_id, Monitor_Summary.Company_Name
HAVING 
    COUNT(1) > 2 AND NewWarnings > 1

我只想选择拥有超过1个NewWarnings的行。我收到错误说无效列，但不确定如何解决此问题。

谢谢，

Answer 1

您需要将基本查询放在子查询或CTE中，以便可以参考NewWarnings列：

;WITH CTE AS
(
    SELECT 
        Monitor_Summary.Company_id AS CompanyId, 
        Monitor_Summary.Company_Name,
        COUNT(1) AS Total,
        (SELECT COUNT(1) 
         FROM MONITOR  
         WHERE ISNULL(MONITOR.IPWarning_ind, 0) = 1
           AND MONITOR.Company_id = Monitor_Summary.Company_ID
           AND MONITOR.Status_ind NOT IN (1,0)) AS NewWarnings      
    FROM 
        Monitor_Summary
    GROUP BY 
        Monitor_Summary.Company_id, Monitor_Summary.Company_Name
)
SELECT 
    CompanyId, 
    Company_Name,
    Total,
    NewWarnings      
FROM
    CTE
WHERE
    Total > 2 AND NewWarnings > 1

Answer 2

SELECT仅在 HAVING执行后才会被评估。因此，您无法在NewWarnings子句中使用HAVING。

解决此问题的一种方法是使用SELECT实现CROSS APPLY子句的相关子查询：

SELECT Monitor_Summary.Company_id AS CompanyId, 
        Monitor_Summary.Company_Name,
        COUNT(1) AS Total,
        x.NewWarnings
FROM Monitor_Summary
CROSS APPLY (
   SELECT COUNT(1) 
   FROM MONITOR  
   WHERE ISNULL(MONITOR.IPWarning_ind, 0) = 1
         AND MONITOR.Company_id = Monitor_Summary.Company_ID
         AND MONITOR.Status_ind NOT IN (1,0)
) AS x(NewWarnings)
WHERE x.NewWarnings > 1
GROUP BY Monitor_Summary.Company_id,Monitor_Summary.Company_Name
HAVING COUNT(1) > 2 

这样您就可以在查询的NewWarnings子句中使用WHERE字段。