Question

我正在围绕这个圈子，并希望有人可以了解如何在第一个返回null时运行第二个查询。

select employee, date, workingrule
case when workingrule is null
then 1 else (select employeenumber, bonusrule from employeelist)
end
from employeedetails

基本上，如果工作规则是空白的，我想找到员工奖金。非常感谢任何指导的帮助。感谢名单

Answer 1

这个适用于SQL Server（因为使用isnull，但可以将其更改为任何特定于RDBMS的查询）：

select
   ed.employee, ed.date,
   isnull(ed.workingrule, el.bonusrule) as [rule]
from employeedetails as ed
    left outer join employeelist as el on el.employeenumber = ed.employeenumber

或者如果你想要两者（应该适用于任何RDBMS）：

select
   ed.employee, ed.date,
   ed.workingrule,
   case when ed.workingrule is null then '1' else el.bonusrule end as bonusrule
from employeedetails as ed
    left outer join employeelist as el on el.employeenumber = ed.employeenumber

Answer 2

select 
  employee, date, Coalesce(workingrule, BonusRule) as Rule 
from 
  employeedetails ed
  left join employeelist el on 
    el.employeenumber = ed.employeenumber

如果第一个结果为null，如何运行第二个SQL查询

2 个答案: