Question

我有以下查询：

select * from 
  (select rownum rnum, p.* from 
    (select DEPARTMENTS.DEPARTMENT_ID, 
     DEPARTMENTS.DEPARTMENT_NAME, 
     DEPARTMENTS.MANAGER_ID,
     EMPLOYEES.EMPLOYEE_ID, 
     EMPLOYEES.FIRST_NAME, 
     EMPLOYEES.LAST_NAME, 
     EMPLOYEES.MANAGER_ID, 
     EMPLOYEES.DEPARTMENT_ID, 
     EMPLOYEES.DETAILS 
     from HR.EMPLOYEES 
     INNER JOIN HR.DEPARTMENTS on
     HR.DEPARTMENTS.DEPARTMENT_ID=EMPLOYEES.DEPARTMENT_ID 
     where EMPLOYEES.EMPLOYEE_ID >= 1) p 
  where rownum <= 4) 
where rnum >= 2

这给了我以下错误：

错误SQL：ORA-00918：列定义不明确 00918. 00000-“列定义不明确”

如果字段的名称不同，则没有错误。例如，此查询是正确的：

select * from 
   (select rownum rnum, p.* from 
     (select DEPARTMENTS.DEPARTMENT_ID, 
       DEPARTMENTS.DEPARTMENT_NAME,
       DEPARTMENTS.MANAGER_ID,
       EMPLOYEES.EMPLOYEE_ID, 
       EMPLOYEES.FIRST_NAME, 
       EMPLOYEES.LAST_NAME, 
       EMPLOYEES.DETAILS 
       from HR.EMPLOYEES
       INNER JOIN HR.DEPARTMENTS on
       HR.DEPARTMENTS.DEPARTMENT_ID=EMPLOYEES.DEPARTMENT_ID 
     where EMPLOYEES.EMPLOYEE_ID >= 1) p
   where rownum <= 4) 
where rnum >= 2

使用分页进行内部联接以及来自具有相同名称的不同表中的字段的正确语法是什么？如何避免在第一次查询中出现ORA-00918错误？

我正在使用Oracle 11g。

Answer 1

在内部查询中使用列别名例如

  -- outer query omitted, table aliases and column aliases added
  select rownum rnum, p.* 
  from (
    select 
      D.DEPARTMENT_ID     did
    , D.DEPARTMENT_NAME   dname
    , D.MANAGER_ID        dmgr
    , E.EMPLOYEE_ID       eid
    , E.FIRST_NAME        efname
    , E.LAST_NAME         elname
    , E.MANAGER_ID        emgr
    , E.DEPARTMENT_ID     edept
    -- , E.DETAILS 
    from HR.EMPLOYEES E
      INNER JOIN HR.DEPARTMENTS D on D.DEPARTMENT_ID = E.DEPARTMENT_ID 
    where E.EMPLOYEE_ID >= 1 ) p
;

-- result
RNUM  DID  DNAME            DMGR  EID  EFNAME     ELNAME       EMGR  EDEPT  
1     10   Administration   200   200  Jennifer   Whalen       101   10     
2     20   Marketing        201   201  Michael    Hartstein    100   20     
3     20   Marketing        201   202  Pat        Fay          201   20     
4     30   Purchasing       114   114  Den        Raphaely     100   30     
5     30   Purchasing       114   115  Alexander  Khoo         114   30     
6     30   Purchasing       114   116  Shelli     Baida        114   30     
7     30   Purchasing       114   117  Sigal      Tobias       114   30     
8     30   Purchasing       114   118  Guy        Himuro       114   30     
9     30   Purchasing       114   119  Karen      Colmenares   114   30   
...

MANAGER_ID和DEPARTMENT_ID列（不带别名）导致您描述的错误（删除注释以获取错误消息）：

  select rownum rnum, p.* 
  from (
    select 
      D.DEPARTMENT_ID
    , D.DEPARTMENT_NAME
    --, D.MANAGER_ID
    , E.EMPLOYEE_ID
    , E.FIRST_NAME
    , E.LAST_NAME
    , E.MANAGER_ID
    --, E.DEPARTMENT_ID
    from HR.EMPLOYEES E
      INNER JOIN HR.DEPARTMENTS D on D.DEPARTMENT_ID = E.DEPARTMENT_ID 
    where E.EMPLOYEE_ID >= 1 ) p
;
-- ORA-00918: column ambiguously defined

在Oracle中将内部连接与分页一起使用的正确语法

1 个答案: