Question

我在Netezza中做了一些QA，我需要比较两个单独的SQL语句中的计数。这是我目前正在使用的SQL

SELECT COUNT(*) AS RECORD_COUNT  
FROM db..EXT_ACXIOM_WUL_FILE  A
LEFT JOIN (select distinct CURRENTLY_OPTED_IN_FL,mid_key from db..F_EMAIL) B
ON A.MID_KEY=B.MID_KEY
MINUS
SELECT COUNT(*)
FROM db..EXT_ACXIOM_WUL_FILE  A

然而，似乎MINUS不能那样工作。当计数匹配时，而不是返回0，这将为Record_count返回null。我基本上将记录计数计算为：

record_count=count1-count2

如果计数相等则为0，否则为差。什么是正确的SQL？

Answer 1

SELECT
(
SELECT COUNT(*) AS RECORD_COUNT  
FROM db..EXT_ACXIOM_WUL_FILE  A
LEFT JOIN (select distinct CURRENTLY_OPTED_IN_FL,mid_key from db..F_EMAIL) B
ON A.MID_KEY=B.MID_KEY
)  -
(
SELECT COUNT(*)
FROM db..EXT_ACXIOM_WUL_FILE  A
) TotalCount

Oracle的MINUS（SQL Server中的EXCEPT）是一个完全不同的动物：）

如果您了解UNION然后考虑集合，您就会理解MINUS / EXCEPT

Answer 2

MINUS设置不同，不适用于算术运算。

你可以做到

SELECT COUNT(*) - (SELECT COUNT(*)
                   FROM   db..EXT_ACXIOM_WUL_FILE A) AS Val
FROM   db..EXT_ACXIOM_WUL_FILE A
       LEFT JOIN (select distinct CURRENTLY_OPTED_IN_FL,
                                  mid_key
                  from   db..F_EMAIL) B
         ON A.MID_KEY = B.MID_KEY

或其他选项

SELECT COUNT(*) - COUNT(DISTINCT A.PrimaryKey) AS Val
FROM   db..EXT_ACXIOM_WUL_FILE A
       LEFT JOIN (select distinct CURRENTLY_OPTED_IN_FL,
                                  mid_key
                  from   db..F_EMAIL) B
         ON A.MID_KEY = B.MID_KEY

Answer 3

我认为这可能就是你要找的东西

    SELECT COUNT(distinct(CURRENTLY_OPTED_IN_FL + F_EMAIL.MID_KEY)) - count(distinct(EXT_ACXIOM_WUL_FILE.MID_KEY))
    FROM EXT_ACXIOM_WUL_FILE 
    LEFT OUTER JOIN F_EMAIL
      ON JOIN F_EMAIL.MID_KEY = EXT_ACXIOM_WUL_FILE.MID_KEY

在SQL中获得两个计数的区别

3 个答案: