【讨论中】百思不得其解，去掉限制条件为什么查不到的记录。

onunix

Mysql Server 5.5

1. select TypeOfBusiness, depOrProfitName, Month,BudgetAccount,MonthBudget from
   
2. (select TypeOfBusiness,depOrProfitName,Month,StatementsSubjects,BudgetAccount,SUM(MonthBudget) as MonthBudget from TotalBudgetOfdepOrProfitName_Adjust_souce where BudgetAccount='奖金' group by TypeOfBusiness,depOrProfitName,Month,StatementsSubjects)
   
3. 
   
4. as a   where  BudgetAccount='奖金' order by TypeOfBusiness , depOrProfitName ;;

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这样可以查出记录，但是去掉第1个 where BudgetAccount='奖金'  反而查不到记录，百思不得其解？谁能解释下么，下面是去掉条件后查不到记录的sql。

1. select TypeOfBusiness, depOrProfitName, Month,BudgetAccount,MonthBudget from
   
2. (select TypeOfBusiness,depOrProfitName,Month,StatementsSubjects,BudgetAccount,SUM(MonthBudget) as MonthBudget from TotalBudgetOfdepOrProfitName_Adjust_souce  group by TypeOfBusiness,depOrProfitName,Month,StatementsSubjects)
   
3. 
   
4. as a   where  BudgetAccount='奖金' order by TypeOfBusiness , depOrProfitName ;;

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按理说，去掉限制条件，查询到的记录只可能更多，为什么反而更少呢？

cenalulu

内查询使用了group by 但是BudgetAccount 却没有使用聚合函数，导致内查询BudgetAccount的值是按照group的物理存储顺序返回第一条。
而SQL1， 由于你限定了BudgetAccount = '奖金'，所以内查询BudgetAccount的结果只能是奖金。