Question

我想根据IN子句示例中的顺序来命令sql查询的结果集：

select * from Employee where EmpID='Eng' and DeptID IN ('Software','Mech','Aero','Civil'),

对于上述查询我想按顺序订购结果集1.软件，2。Mech，3。Aero，4。Civil

Answer 1

在Oracle中，使用instr()或case：

select *
from Employee
where EmpID='Eng' and DeptID IN ('Software','Mech','Aero','Civil')
order by instr('Software,Mech,Aero,Civil', DeptId)

这也适用于DB2。

case表单也适用于两个数据库，但更长：

order by (case DeptID when 'Software' then 1
                      when 'Mech' then 2
                      when 'Aero' then 3
                      when 'Civil' then 4
          end)

Answer 2

您可以维护虚拟列中的顺序并使用表中的输入或使用with子句

 with subject as 
 (select 1 ord,'Software' as sub from dual
  union 
  select 2 ord,'Mech' as sub from dual
  union
  select 3 ord,'Aero' as sub from dual
  union
  select 4 ord,'Civil' as sub from dual)

select e.* from Employee,subject
where EmpID='Eng'
and DeptID=subject.sub
order by subject.ord

根据IN子句中给出的顺序对查询结果进行排序

2 个答案: