Swap column name from MGR to MGR_NAME

Hi,

Empno has number data type, not null. MRG_NAME has number data type.

I changed this:

ALTER TABLE EMP RENAME COLUMN MGR TO MGR_NAME;

SELECT empno, ename, hiredate, mgr_name(empno)
FROM emp;

I want MGR_Name to display with empno.

Return, I got "MGR_NAME" invalid identifier.

Any advice is appreciated?
LVL 1
suredazzleAsked:
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suredazzleAuthor Commented:
After reading my book.
Verified the result is correct.

Need to add new column.


SQL> SELECT empno, ename, hiredate, mgr_name
FROM emp
WHERE empno NOT IN
    (SELECT mgr_name FROM emp
    WHERE mgr_name IS NOT NULL);

==========================================

     EMPNO ENAME      HIREDATE        MGR_NAME
---------- ---------- --------- ----------
      7782 CLARK      09-JUN-81       7839
      7654 MARTIN     28-SEP-81       7698
      7499 ALLEN      20-FEB-81       7698
      7844 TURNER     08-SEP-81       7698
      7900 JAMES      03-DEC-81       7698
      7521 WARD       22-FEB-81       7698
      7369 SMITH      17-DEC-80       7902
      7876 ADAMS      12-JAN-83       7788
      1456 JOHN SMITH 01-JAN-02       7566



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suredazzleAuthor Commented:
Insert row into emp with deptno null.

Foreign key constraint of deptno in emp.

Best to re-create table emp2 and emp2.self_key. Delete constraint emp_foreign_key line.

Also, you can disable the column constraint.
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suredazzleAuthor Commented:

Use self-join for 2 diff. table aliases, treat EMP like 2 separate tables.
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