Question

我很熟悉SQL和循环，特别需要一些帮助解决以下问题。

我有一张这样的表：

SpotID EventID MaxTemp

123    1  45
236    1  109
69     1  18
123    2  216
236    2  29
69     2  84
123    3  91
236    3  457
69     3  280

我想生成一个包含以下输出的新表：

SpotID Over30 Over70 Over100 

123    3      2      1
236    2      2      2  
69     2      2      1

所以我所追求的是不同EventID的温度超过每个SpotID 30,70和100的限制的次数。

有没有办法用循环来做到这一点？我的数据集显然更大，我很好奇我是否可以使用有效的东西。

非常感谢你。

迈克

Answer 1

您只需要条件聚合：

select spotid,
       sum(case when maxtemp > 30 then 1 else 0 end) as over_30,
       sum(case when maxtemp > 70 then 1 else 0 end) as over_70
       sum(case when maxtemp > 100 then 1 else 0 end) as over_100
from likethis
group by spotid;

Answer 2

对上一篇文章进行了一次小修改，我的版本仅在每个临时范围内计算，否则较低的临时值将计算该范围内的大多数临时值而不是临时值。

 DECLARE @DATA TABLE (
    SpotID INT,
    EventID INT,
    MaxTemp INT
    )

 INSERT INTO @DATA VALUES
    (123, 1, 45 ),
    (236, 1, 109),
    (69 , 1, 18 ),
    (123, 2, 216),
    (236, 2, 29 ),
    (69 , 2, 84 ),
    (123, 3, 91 ),
    (236, 3, 457),
    (69 , 3, 280)

 SELECT 
    SpotID,
    SUM(CASE WHEN MaxTemp >  30  AND MaxTemp < 70  THEN 1 ELSE 0 END) AS OVER_30,
    SUM(CASE WHEN MaxTemp >= 70  AND MaxTemp < 100 THEN 1 ELSE 0 END) AS OVER_70,
    SUM(CASE WHEN MaxTemp >= 100 THEN 1 ELSE 0 END) AS OVER_100
 FROM 
    @DATA
 GROUP BY
    SpotID

Answer 3

如果您只是想学习如何使用循环......

 DECLARE @DATA TABLE (
    SpotID INT,
    EventID INT,
    MaxTemp INT
    );

 DECLARE @NEWDATA TABLE (
    SpotID INT,
    T30 INT,
    T90 INT,
    T100 INT
    );

 DECLARE 
    @SPOT AS INT,
    @T30 AS INT,
    @T90 AS INT,
    @T100 AS INT;


 INSERT INTO @DATA VALUES
    (123, 1, 45 ),
    (236, 1, 109),
    (69 , 1, 18 ),
    (123, 2, 216),
    (236, 2, 29 ),
    (69 , 2, 84 ),
    (123, 3, 91 ),
    (236, 3, 457),
    (69 , 3, 280);


 DECLARE STATION CURSOR FOR SELECT SpotID FROM @DATA GROUP BY SpotID;
 OPEN STATION;
 FETCH NEXT FROM STATION INTO @SPOT;
 WHILE @@FETCH_STATUS = 0
 BEGIN
    SET @T30 = 0;
    SET @T90 = 0;
    SET @T100 = 0;

    SELECT 
    @T30 = SUM(CASE WHEN MaxTemp >  30  AND MaxTemp < 70  THEN 1 ELSE 0 END),
    @T90 = SUM(CASE WHEN MaxTemp >= 70  AND MaxTemp < 100 THEN 1 ELSE 0 END),
    @T100 = SUM(CASE WHEN MaxTemp >= 100 THEN 1 ELSE 0 END)
    FROM @DATA WHERE SpotID = @SPOT

    INSERT INTO @NEWDATA VALUES (@SPOT,@T30,@T90,@T100)
    FETCH NEXT FROM STATION INTO @SPOT;
 END;

 CLOSE STATION;
 DEALLOCATE STATION;

 SELECT * FROM @NEWDATA

我不会写所请求的代码，但是这个例子展示了如何创建表变量，一个简单的循环游标，以及写入加载到新表中的变量的答案。

许多活动部件，但它可以让你深入了解循环。

在SQL中使用循环来填充表（SQL Server）

3 个答案: