Question

对于前。我的问题：

select * 
from 
    (SELECT distinct b.lname||' '||b.fname as "Manager",b.EMPID as "Mgrid" 
     from EMPLOYEE1) a, 
    (select lname,fname,empid from EMPLOYEE1) b 
where b.EMPID=a.MGRID)

正在抓取

Manager           Mgrid    
----------------  -------- 
Farooque Umer     104      
Sontireddy Kiran  107      
Chopra Bhupendra  103

但我不能写：

select Manager, Mgrid 
from 
    (select distinct b.lname||' '||b.fname as "Manager",b.EMPID as "Mgrid" 
    from EMPLOYEE1) a, 
    (select lname,fname,empid 
    from EMPLOYEE1) b 
where b.EMPID=a.MGRID)

错误：

[错误]脚本行：1-1 -------------------------- ORA-00904：“MGRID”：标识符无效

Answer 1

因为一旦你开始用双引号括起名字，比如“Mgrid”，就会出现区分大小写的情况。所以不要。这样做：

select Manager, Mgrid 
from 
    (select distinct b.lname||' '||b.fname as Manager,b.EMPID as Mgrid 
    from EMPLOYEE1) a, 
    (select lname,fname,empid 
    from EMPLOYEE1) b 
where b.EMPID=a.MGRID)

或者如果你真的喜欢区分大小写的名字，你必须这样做：

select "Manager", "Mgrid" 
from 
    (select distinct b.lname||' '||b.fname as "Manager",b.EMPID as "Mgrid" 
    from EMPLOYEE1) a, 
    (select lname,fname,empid 
    from EMPLOYEE1) b 
where b.EMPID=a."Mgrid")

Answer 2

您应该只在顶级选择中应用化妆品字段命名 - 所有其他标识符应保留为有效的Oracle标识符。

select manager as "Manager", mgrid as "Mgrid" 
from 
    (select distinct b.lname||' '||b.fname as manager, b.EMPID as mgrid
    from EMPLOYEE1) a, 
    (select lname,fname,empid 
    from EMPLOYEE1) b 
where b.EMPID=a.MGRID)

Answer 3

除了引号之外，我认为你的帖子还包含一个比需要多的括号：

select Manager, Mgrid 
from 
    (select distinct b.lname||' '||b.fname as Manager,b.EMPID as Mgrid 
    from EMPLOYEE1 a, 
    (select lname,fname,empid 
    from EMPLOYEE1) b 
    where b.empid =a.Mgrid)

当我们从别名中获取值时，为什么在Oracle中我们无法将列指定为别名？

3 个答案: