Problem: query to find employees at one plant for specified year

Question

Problem: how to determine if an employee was working at a specific plant during a specific year using this limited amount of data in a "job changes" table. No matter what I've tried, I keep getting the wrong number of records and it's driving me nuts. I thought this would be a simple query but it's not (for me anyway!) so I need a "clue" to point me in the right direction. Help? :-)
Sample records:
EMPLID  PLANT   EFF_DATE    HIRE_DATE   TERM_DATE
123456  23      01-JAN-00   22-MAR-88   NULL
123456  29      30-JUL-02   22-MAR-88   NULL
123456  22      21-AUG-03   22-MAR-88   NULL
456789  29      11-JUL-01   11-JUL-01   NULL
456789  22      30-JUL-03   11-JUL-01   NULLFor example, how do I write the query so that employee 123456 will show up for years 1999 and 2001 in plant 23?

Answer 1

Here is an example:
SQL> SELECT * FROM EMP;
    EMPLID      PLANT EFF_DATE    HIRE_DATE   TERM_DATE
    123456         23 01-JAN-2000 22-MAR-1988
    123456         29 30-JUL-2002 22-MAR-1988
    123456         22 21-AUG-2003 22-MAR-1988
    456789         29 11-JUL-2001 11-JUL-2001
    456789         22 30-JUL-2003 11-JUL-2001
5 rows selected.
SQL> SELECT A.EMPLID,A.PLANT,A.EFF_DATE,A.END_DATE FROM
  2  (SELECT EMPLID,PLANT,EFF_DATE,LEAD(EFF_DATE,1) OVER(ORDER BY EMPLID,EFF_DATE) -1 END_DATE,
  3  HIRE_DATE FROM EMP
  4  WHERE EMPLID=123456
  5  ORDER BY EMPLID) A
  6  WHERE A.EFF_DATE >= TO_DATE('01-JAN-1999','DD-MON-YYYY')
  7  AND A.EFF_DATE <= TO_DATE('31-DEC-2001','DD-MON-YYYY')
  8  AND TO_DATE('31-DEC-2001','DD-MON-YYYY') <= END_DATE;
    EMPLID      PLANT EFF_DATE    END_DATE
    123456         23 01-JAN-2000 29-JUL-2002
1 row selected.