Case or if condition in sql

Question

I need to load distinct enames to target table emp.
1st condition: check the latest mod_time of ename whether active or inactive status
2nd condition: if last mod time is same for one ename check emp_status='ACTIVE' load active record
3rd condition if the ACTIVE records are more than on take max(emp_id)
Emp source table
emp_id  ename mod_date         emp_status    
103     MARY     22-JAN-2012       INACTIVE
104     MARY      21-JAN-2012      ACTIVE
100          john    21-JAN-2012        ACTIVE
101          john    21-JAN-2012       INACTIVE
102          john    21-JAN-2012        ACTIVE
105     JUHI     21-JAN-2012       INACTIVE
106     JUHI      21-JAN-2012      ACTIVE
107     CHEN     21-JAN-2012       INACTIVE
108     CHEN      22-JAN-2012      ACTIVE
109     james     21-JAN-2012       INACTIVE
110     james      22-JAN-2012      INACTIVE
EXPECTED OUTPUT emp target
emp_id  ename mod_date         emp_status    
103     MARY     22-JAN-2012       INACTIVE --take latest mod_time  first priority check.
102          john    21-JAN-2012        ACTIVE --first check latest mod_time. since two active records with the same mod_time then take max(emp_id)
106     JUHI      21-JAN-2012      ACTIVE  --two records with same mod_time with status active and inactive. take active record.
108     CHEN      22-JAN-2012      ACTIVE --active is the latest mod time
110     james      22-JAN-2012      INACTIVE --  two records with same mod_time with status active take max(emp_id)---------------------------
how can i implement this logic with one sql command and insert into emp_target table
I should have only one record per employee from source
Edited by: choti on Feb 21, 2013 4:58 PM

Answer 1

Not sure that this is the most elegant way to do this, but...
WITH emp AS
  SELECT 103 emp_id, 'MARY' ename, '22-JAN-2012' mod_date, 'INACTIVE' emp_status FROM dual UNION ALL
  SELECT 104, 'MARY', '21-JAN-2012', 'ACTIVE' FROM dual UNION ALL
  SELECT 100, 'john', '21-JAN-2012', 'ACTIVE' FROM dual UNION ALL
  SELECT 101, 'john', '21-JAN-2012', 'INACTIVE' FROM dual UNION ALL
  SELECT 102, 'john', '21-JAN-2012', 'ACTIVE' FROM dual UNION ALL
  SELECT 105, 'JUHI', '21-JAN-2012', 'INACTIVE' FROM dual UNION ALL
  SELECT 106, 'JUHI', '21-JAN-2012', 'ACTIVE' FROM dual UNION ALL
  SELECT 107, 'CHEN', '21-JAN-2012', 'INACTIVE' FROM dual UNION ALL
  SELECT 108, 'CHEN', '22-JAN-2012', 'ACTIVE' FROM dual UNION ALL
  SELECT 109, 'james','21-JAN-2012', 'INACTIVE' FROM dual UNION ALL
  SELECT 110, 'james','22-JAN-2012', 'INACTIVE' FROM dual
emp1 AS (
  SELECT emp_id, ename, mod_date, emp_status, MAX(mod_date) OVER (PARTITION BY ename) max_mod_date
    FROM emp
emp2 AS (
  SELECT emp_id, ename, mod_date, emp_status, MIN(emp_status) OVER (PARTITION BY ename, mod_date) min_emp_status
    FROM emp1
    WHERE mod_date = max_mod_date
emp3 AS (
SELECT emp_id, ename, mod_date, emp_status, MAX(emp_id) OVER (PARTITION BY ename, mod_date, emp_status) max_emp_id
  FROM emp2
  WHERE min_emp_status = emp_status
emp4 AS (
SELECT *
  FROM emp3
  WHERE max_emp_id = emp_id)
SELECT emp_id, ename, mod_date, emp_status
  FROM emp4
    EMP_ID ENAME MOD_DATE    EMP_STATUS
       103 MARY  22-JAN-2012 INACTIVE 
       102 john  21-JAN-2012 ACTIVE   
       106 JUHI  21-JAN-2012 ACTIVE   
       108 CHEN  22-JAN-2012 ACTIVE   
       110 james 22-JAN-2012 INACTIVE  5 rows selected.
Note: I manually re-ordered the result set so that it matches your expected results.
Edited by: user1983440 on Feb 21, 2013 10:55 PM