sql - Oracle sql中使用countif计算每一行

Question

我可以知道是否有像Excel countif中那样的sql语句来根据条件计算高、中、低。

例如，下表显示了在 high 中使用 countif，我们可以看到每行 High 多少、low 多少、medium 多少

ID   Name     Value1     Value2     Value3    ValueN   High   Medium  Low
---  -------  ---------  ---------  --------  -------  -----  ------  ------
1    A        High       High       Low       Medium   2      1       1 
2    AB       Low        Medium     Low       High     1      1       2
3    ABC      High       Low        Low       High     2      0       2

Answer 1

您可以先使用UNPIVOT数据，然后进行条件聚合:

SELECT ID, Name,
       COUNT(CASE WHEN val = 'High' THEN 1 END)   AS High,
       COUNT(CASE WHEN val = 'Medium' THEN 1 END) AS Medium,
       COUNT(CASE WHEN val = 'Low' THEN 1 END)    AS Low
FROM tab
UNPIVOT( val FOR col_name IN (Value1, Value2, Value3, ValueN)) unpvt
GROUP BY ID, Name

LiveDemo

要处理更多列，只需将它们添加到:

val FOR col_name IN (Value1, Value2, Value3, ValueN)

---

最终查询包含原始选项卡中的所有列:

SELECT t.*, sub.High, sub.Medium, sub.Low
FROM tab t
JOIN (SELECT ID, Name, 
         COUNT(CASE WHEN val = 'High' THEN 1 END)   AS High,
         COUNT(CASE WHEN val = 'Medium' THEN 1 END) AS Medium,
         COUNT(CASE WHEN val = 'Low' THEN 1 END)    AS Low
      FROM tab
      UNPIVOT( val FOR col_name IN (Value1, Value2, Value3, ValueN)) unpvt
      GROUP BY ID, Name) sub
  ON t.ID = sub.ID

LiveDemo2

输出:

╔════╦══════╦════════╦════════╦════════╦════════╦══════╦════════╦═════╗
║ ID ║ Name ║ Value1 ║ Value2 ║ Value3 ║ ValueN ║ High ║ Medium ║ Low ║
╠════╬══════╬════════╬════════╬════════╬════════╬══════╬════════╬═════╣
║  1 ║ A    ║ High   ║ High   ║ Low    ║ Medium ║    2 ║      1 ║   1 ║
║  2 ║ AB   ║ Low    ║ Medium ║ Low    ║ High   ║    1 ║      1 ║   2 ║
║  3 ║ ABC  ║ High   ║ Low    ║ Low    ║ High   ║    2 ║      0 ║   2 ║
╚════╩══════╩════════╩════════╩════════╩════════╩══════╩════════╩═════╝