如何在SQL Server中选择行到列

Question

我不知道有没有迭代游标和填充临时表的可能性。 我很难选择如下所示的数据：

+----------+-----------+-----------+
|TypeName  | AlarmType | AlarmCount|
+----------+-----------------------+
|Antibody  | 1         | 2         |
|Bacterium | 1         | 2         |
|Bacterium | 3         | 2         |
|CellLine  | 1         | 2         |
+----------+-----------+-----------+

变成这样的结果（有3种不同的AlarmType，但列出了2种）：

+----------+-------+-------+-------+
|TypeName  | Alarm1| Alarm2| Alarm3|
+----------+-------+-------+-------+
|Antibody  | 2     | 0     | 0     |
|Bacterium | 2     | 0     | 2     |
|CellLine  | 2     | 0     | 0     |
+----------+-------+-------+-------+

如您所见， AlarmCount现在显示在对应的AlarmType ，该列现在在此栏中。 如果不可能做到这一点，那么“没有光标就无法做到”也是一个很好的答案。

这是我的小提琴

Answer 1

您可以通过两种方式执行此操作。

使用Conditional Aggregate将AlarmType为列并在每个AlarmType下显示相应的AlarmCount 。

SELECT TypeName,
       Max(CASE WHEN AlarmType = 1 THEN AlarmCount ELSE 0 END) Alarm1,
       Max(CASE WHEN AlarmType = 2 THEN AlarmCount ELSE 0 END) Alarm2,
       Max(CASE WHEN AlarmType = 3 THEN AlarmCount ELSE 0 END) Alarm3
FROM   alarms
GROUP  BY TypeName

也可以通过Pivot完成

SELECT TypeName,
       Isnull([1], 0) Alarm1,
       Isnull([2], 0) Alarm2,
       Isnull([3], 0) Alarm3
FROM   (SELECT *
        FROM   alarms) a
       PIVOT (Max(AlarmCount)
             FOR AlarmType IN([1],
                              [2],
                              [3])) piv 

注意：如果您不知道AlarmType列，则可能必须使用Dynamic Pivot

Answer 2

这是UNION方法：

SELECT Alarm_Type_Name, SUM(Alarm1) AS Alarm1, SUM(Alarm2) AS Alarm2, SUM(Alarm3) AS Alarm3 FROM
(
SELECT TypeName AS Alarm_Type_Name, SUM(AlarmCount) AS Alarm1, 0 AS Alarm2, 0 AS Alarm3 FROM ALARM_TEMP
WHERE AlarmType = 1
GROUP BY TypeName, AlarmCount

UNION 

SELECT TypeName AS Alarm_Type_Name, 0 AS Alarm1, SUM(AlarmCount) AS Alarm2, 0 AS Alarm3 FROM ALARM_TEMP
WHERE AlarmType = 2
GROUP BY TypeName, AlarmCount

UNION 

SELECT TypeName AS Alarm_Type_Name, 0 AS Alarm1, 0 AS Alarm2, SUM(AlarmCount) AS Alarm3 FROM ALARM_TEMP
WHERE AlarmType = 3
GROUP BY TypeName, AlarmCount

)a

GROUP BY Alarm_Type_Name

希望对您有所帮助。