Question

我都使用subquery [Below]来确定百分比。但是我需要一个没有子查询的查询。谁能帮我，如何使用联接来计算百分比？

已使用查询

def unreliable_method(item) do
  # Do something with `item`
  :ok
rescue
  _err ->
    Logger.error("Failed for item: #{inspect(item)}")
    Logger.error(inspect(__STACKTRACE__))
    {:error, :processing_failed}
end

Answer 1

“我需要一个没有子查询的查询。”

答案：

SELECT Count(*) All_count
     , SUM(CASE WHEN N.id_membid_claimid_c IS NULL THEN 1 else 0 end) as Dropped_count
     , SUM(CASE WHEN N.id_membid_claimid_c IS NULL THEN 1 else 0 end) * 1.0 / Count(*) as Dropping_Percentage
FROM pfo_bhi_new N 
RIGHT JOIN pfo_bhi_old o ON o.id_membid_claimid_c = N.id_membid_claimid_c

说明：

使用有关内容的假设来审查主查询：

SELECT Count(*) Dropped_count, '1' b 
FROM pfo_bhi_new N 
RIGHT JOIN pfo_bhi_old o ON o.id_membid_claimid_c = N.id_membid_claimid_c 
WHERE N.id_membid_claimid_c IS NULL

应为您提供pfo_bhi_old中未出现在pfo_bhi_new中的记录数。这里的假设是您需要基于现有的右连接进行总计。所有匹配和不匹配的记录。

因此，可以通过删除where子句来计算所有现有记录， COUNT（*）会给您总计。

接下来，您要计算没有匹配项的数目，这将使您使用where子句获得的值“滴落计数”，即id_membid_claimid_c为null的那些位置，即 SUM（CASE当N.id_membid_claimid_c为NULL时，则返回1，否则0结束）。换句话说，只有在id_membid_claimid_c字段为null时，才会将1加到总和上，否则它将加零（0）。

我将分子乘以1.0，以强制SQL Server使用十进制值，并使查询更易于阅读。

如果需要使用小数（16,9）作为结果，则应该是这样。

SELECT Count(*) All_count
     , SUM(CASE WHEN N.id_membid_claimid_c IS NULL THEN 1 else 0 end) as Dropped_count
     , SUM(CASE WHEN N.id_membid_claimid_c IS NULL THEN 1 else 0 end) * 1.0 / Count(*) as Dropping_Percentage

     , CAST(SUM(CASE WHEN N.id_membid_claimid_c IS NULL THEN 1 else 0 end) AS DECIMAL(16,9)) / CAST(Count(*) AS DECIMAL(16,9)) as Dropping_Pct_16_9

FROM pfo_bhi_new N 
RIGHT JOIN pfo_bhi_old o ON o.id_membid_claimid_c = N.id_membid_claimid_c

更改子查询以加入

1 个答案: