带有分组依据和案例陈述的子查询

Question

我有两个表，一个是“ 国家”表，另一个是“ 阈值表”。

国家表具有像这样的列和数据：

ID Country Count Year
00001 India 200 2011
00001 India 400 2013
00001 Japan 1000 2011
00001 Japan 550 2013
00001 China 400 2011

阈值表具有如下数据：

ID Low Value High Value
00001 500 1000

这意味着如果Count >= 500则为Low ，如果Count > 500 and < 1000为Medium，而Count >= 1000则为High 。

我想要这样的结果：

Country Count Threshold Low Value High Value
India 600 Medium 500 1000
Japan 1550 High 500 1000
China 400 Low 500 1000

所以我想写一个SQL query 。

我已经在使用此查询：

SELECT C.Country,C.Count
,CASE WHEN C.Count <= T.Low_Value THEN 'Low' WHEN C.Count BETWEEN T.High_Value AND T.Low_Value THEN 'Medium' ELSE 'High' END AS Threshold,
T.Low_Value, T.High_Value FROM 
(SELECT ID,Country,Sum(Count) AS Count 
FROM Country 
WHERE ID=00001 
GROUP BY ID,Country) C 
JOIN Threshold T 
ON C.ID = T.ID

但是此查询给出了错误。

谁能建议我如何实现这一目标？

我正在使用Oracle

错误是ORA-00979：不是GROUP BY表达式

**This query is just for representation**

Answer 1

COUNT是保留字。 选择其他别名或在别名周围使用双引号。

SELECT C.Country,
       C."Count",
       CASE WHEN C."Count" <= T.Low_Value THEN 'Low'
            WHEN C."Count" BETWEEN T.High_Value AND T.Low_Value THEN 'Medium'
            ELSE 'High' END AS Threshold,
       T.Low_Value,
       T.High_Value
FROM   (
  SELECT ID,Country,Sum("Count") AS "Count"
  FROM Country 
  WHERE ID=00001 
  GROUP BY ID,Country
) C 
JOIN Threshold T 
ON C.ID = T.ID

Answer 2

可以通过使用以下命令完成：

SELECT Country
      ,Total
      ,CASE WHEN Total <= Low_Value THEN 'Low'
            WHEN Total BETWEEN Low_Value AND High_Value THEN 'Medium'
        ELSE 'High' END AS Threshold
      FROM (SELECT ID
          ,Country
          ,Low_Value
          ,High_Value
          ,SUM(Count) Total
         FROM (SELECT C.ID
             ,C.Country
             ,C.Count
             ,T.Low_Value
             ,T.High_Value
           FROM Country C JOIN Threshold T
           ON C.ID=T.ID
           WHERE C.ID =00001)
        GROUP BY Country,Low_Value,High_Value)