处理嵌套查询mysql中的NULL值 [英] Handle NULL value in nested query mysql

问题描述

我正在尝试使用以下查询将 NULL 替换为 0.但是当结果不是 NULL 时，它只获取不是要求的最大值.我尝试删除 max 函数，但它返回 NULL.

I am trying to replace NULL with 0 with the below query. but when the result is not NULL, it fetches onlY the max value which is not the requirement. I tried removing max function but it returns NULL.

下面是查询.

select (select coalesce(max(QTIB_REQ_), 0) 
  from qb_requisitions_all 
 where QTIB_REQ_ IN ($Req_disabled_WA) 
   and CLIENT___BENCH___NON_BILLABLE IN ( 'Non Billable', 'Non-Billable', 'NonBillable') 
   and DATEDIFF(CURDATE(),TARGET_FILL_DATE) < 30 
   and DATEDIFF(CURDATE(),TARGET_FILL_DATE) > 0
   )

推荐答案

尝试在最大聚合内添加 IFNULL

Try adding IFNULL inside max aggregate

select (select max(IFNULL(QTIB_REQ_, 0))
from qb_requisitions_all 
where QTIB_REQ_ IN ($Req_disabled_WA) and CLIENT___BENCH___NON_BILLABLE IN ( 'Non 
 Billable', 'Non-Billable', 'NonBillable') 
 and DATEDIFF(CURDATE(),TARGET_FILL_DATE) < 30 
 and DATEDIFF(CURDATE(),TARGET_FILL_DATE) > 0

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