Question

我在SQL 2005表中有以下数据模式：

MPAN, Date, Reading1, Reading2, Reading3,......, Reading48

134, 21/05/11, , ,0.345 ,......,0.789

134, 22/05/11, , , ,......, 0.467

456, 21/05/11, , , , , 1.234

456, 22/05/11, 0.009 , , 0.534,......

223, 21/05/11, , , ,........, 3.345

223, 22/05/11, 3.223, 1.234, , , ....,0.989

对于每个记录行，有不同数量的字段缺少数据。我怎样才能找出每行丢失数据的文件数（按MPAN和日期分组）。在Google上进行了搜索，似乎有人建议针对类似案例的存储过程？

请帮忙吗？

Answer 1

通常的做法是使用CASE：

SELECT CASE WHEN field_1 IS NULL THEN 1 ELSE 0 END
       + CASE WHEN field_2 IS NULL THEN 1 ELSE 0 END
       + ... AS total_nulls,
       COUNT(*) as num_rows
FROM table 
GROUP BY total_nulls;

使用您问题中的分组和字段名称：

SELECT MPAN, Date,
       SUM(CASE WHEN Reading1 IS NULL THEN 1 ELSE 0 END
       + CASE WHEN Reading2 IS NULL THEN 1 ELSE 0 END
       + ... ) AS total_nulls
FROM table 
GROUP BY MPAN, Date;

Answer 2

SELECT
  MPAN,
  Date,
  NullCount = COUNT(*) * 48
    - COUNT(Reading1)
    - COUNT(Reading2)
    - COUNT(Reading3)
    …
    - COUNT(Reading48)
FROM atable
GROUP BY MPAN, Date

Answer 3

使用case语句计算总和：

select MPAN, date, sum(null_cnt) from (
  select MPAN, date,
  (case when val1 is null then 1 else 0 end) +
  (case when val2 is null then 1 else 0 end) + ...
  (case when val48 is null then 1 else 0 end) null_cnt
  from ...
) group by MPAN, date

Answer 4

我担心你不得不做一些丑陋的事情

select MPAN, Date, (
    CASE WHEN Reading1 is null then 1 else 0 end +
    CASE WHEN Reading2 is null then 1 else 0 end +
    CASE WHEN Reading3 is null then 1 else 0 end +
    CASE WHEN Reading4 is null then 1 else 0 end +
    ... +
    CASE WHEN Reading48 is null then 1 else 0 end
) as CountOfNulls

from YourTable

Answer 5

如果你可以改变架构，我要做的第一件事就是把它分成三个表：

带有ID和名称的'读数'，值

ID  Name
1   Reading1
2   Reading2
...
48  Reading48

这使您可以轻松添加更多内容。

接下来是一个'MPAN'表，其中包含带有ID，MPAN和日期的MPAN：

ID MPAN Date
1  134  21/05/11
2  134  22/05/11

最后，一个“得分”表格将两者联系起来，并将得分与ReadingID，MPANID和得分相对应：

MPANID ReadingID Score
1      3         0.345
1      48        0.789
2      48        0.467

然后，您可以让关系数据库执行他们最擅长的操作并利用这些关系。例如，此查询将获得具有Reading2分数的所有MPAN：

SELECT MPAN.*, Scores.Score
  FROM MPAN
  JOIN Scores ON Scores.MPANID = MPAN.ID
             AND Scores.ReadingID = 2

Answer 6

select MPAN,
       Date,
       sum
          (
            case when Reading1 is null then 1 else 0 end +
            case when Reading2 is null then 1 else 0 end +
            case when Reading3 is null then 1 else 0 end
          ) as NullCount
from T
group by MPAN,
         Date

Answer 7

使用此

select 
MPAN, Date,
coalesce(isnull(reading1,0)+isnull(reading2,0)+isnull(reading3,0)+isnull(reading4,0),0) 
from 
tablename

如何计算多列中的空值

7 个答案: