当列中的行为空时，ORACLE显示计数为零

Question

我有一个包含许多列的表，我计算列上的特定名称，如果该名称不在列表中，我想将其显示为零，但不能进入列表。

SELECT Names, COUNT (*)
FROM NAMESTABLE
WHERE names IN
                ('Jenny',
                 'Penny',
                 'George',
                 'James',
                 'Jessica',
                 'Monica',
                 'Erica')
             AND  
adeddate BETWEEN '2014/10/15' AND '2014/10/16' 
GROUP BY names 

---

NAMES  ||   COUNT(*)
Jenny  ||   33
Penny  ||   4
George ||   25
James  ||   87

所以我想杰西卡，莫妮卡，埃里卡作为ZERO甚至这些名字都不在COLUMN

Names    ||  Count(*)
Jenny    ||    33
Penny    ||     4
George   ||    25 
James    ||    87
Jessica  ||     0
Monica   ||     0
Erica    ||     0

nvl(count(*),0)不起作用

Answer 1

您可以按名称对结果进行分组，然后将结果left join到您的名称表中以填充空白：

SELECT    rn.name, NVL(cnt, 0)
FROM      (SELECT 'Jenny' AS name FROM dual
           UNION ALL
           SELECT 'Penny' FROM dual
           UNION ALL
           SELECT 'George' FROM dual
           UNION ALL
           SELECT 'James' FROM dual
           UNION ALL
           SELECT 'Jessica' FROM dual
           UNION ALL
           SELECT 'Monica' FROM dual
           UNION ALL
           SELECT 'Erica' FROM dual) rn
LEFT JOIN (SELECT   name, COUNT(*) AS cnt
           FROM     namestable
           WHERE    adeddate BETWEEN '2014/10/15' AND '2014/10/16' 
           GROUP BY name) n ON n.name = rn.name

Answer 2

然后你必须使用其他语法：

SELECT t.Names, COUNT(n.Names)
FROM (
  SELECT 'Jenny' AS names FROM DUAL UNION ALL
  SELECT 'Penny' FROM DUAL UNION ALL
  SELECT 'George' FROM DUAL UNION ALL
  SELECT 'James' FROM DUAL UNION ALL
  SELECT 'Jessica' FROM DUAL UNION ALL
  SELECT 'Monica' FROM DUAL UNION ALL
  SELECT 'Erica' FROM DUAL
) t
LEFT OUTER JOIN NAMESTABLE n
  ON n.names = t.names AND n.adeddate BETWEEN '2014/10/15' AND '2014/10/16'
GROUP BY t.names

Answer 3

这应该适用于CTE ..

WITH CTE AS
(SELECT 'Jenny' Names FROM dual UNION ALL
 SELECT 'Penny' FROM dual UNION ALL
 SELECT 'George' FROM dual UNION ALL
 SELECT 'James' FROM dual UNION ALL
 SELECT 'Jessica' FROM dual UNION ALL
 SELECT 'Monica' FROM dual UNION ALL
 SELECT 'Erica' FROM dual)
SELECT CTE.names, coalesce(count(NT.Names),0)
FROM  CTE
LEFT JOIN NAMESTABLE NT 
  on CTE.Names = NT.Names
 and adeddate BETWEEN '2014/10/15' AND '2014/10/16' 
GROUP BY CTE.Names

Answer 4

您可以创建一个包含所有有效名称的表，例如valid_names表。然后使用outerjoin加入你的namestable。例如：

select valid_names.name, count(1) 
from namestable, valid_names
where valid_names.name=namestable.name (+)
group by valid_names.name
order by valid_names.name;