Without Decode or Case

Question

I have emp_allocation table. It has data as below
EMPID     YEAR      MONTH
X     2006     JAN
X     2006     MAR
Y     2006     JAN
Y     2006     FEB
Y     2006     MAR
I want SQL Query(Without Decode or Case) which will give output as below
EMPID     YEAR      JAN     FEB     MAR      APR     JUN     JUL
X     2006     Y     N     Y
Y     2006     Y     Y     Y

Answer 1

Why you'd want to do it this way I do not know, but if you insist...
SQL> ed
Wrote file afiedt.buf
  1  WITH t AS (select 'X' AS EMPID, 2006 AS YEAR, 'JAN' AS MONTH FROM DUAL UNION ALL
  2             select 'X', 2006, 'MAR' FROM DUAL UNION ALL
  3             select 'Y', 2006, 'JAN' FROM DUAL UNION ALL
  4             select 'Y', 2006, 'FEB' FROM DUAL UNION ALL
  5             select 'Y', 2006, 'MAR' FROM DUAL)
  6  -- END OF TEST DATA
  7  SELECT EMPID, YEAR, NVL(MAX(JAN),'N') AS JAN, NVL(MAX(FEB),'N') AS FEB, NVL(MAX(MAR),'N') AS MAR, NVL(MAX(APR),'N') AS APR
  8  FROM
  9  (
10    SELECT EMPID, YEAR, 'Y' AS JAN, NULL AS FEB, NULL AS MAR, NULL AS APR FROM t WHERE MONTH = 'JAN' UNION ALL
11    SELECT EMPID, YEAR, NULL AS JAN, 'Y' AS FEB, NULL AS MAR, NULL AS APR FROM t WHERE MONTH = 'FEB' UNION ALL
12    SELECT EMPID, YEAR, NULL AS JAN, NULL AS FEB, 'Y' AS MAR, NULL AS APR FROM t WHERE MONTH = 'MAR' UNION ALL
13    SELECT EMPID, YEAR, NULL AS JAN, NULL AS FEB, NULL AS MAR, 'Y' AS APR FROM t WHERE MONTH = 'APR'
14  )
15  GROUP BY EMPID, YEAR
16* ORDER BY 1,2
SQL> /
E       YEAR J F M A
X       2006 Y N Y N
Y       2006 Y Y Y N
SQL>