SQL Results group by month

Question

I\'m trying to return some results spread over a rolling 12 month period eg:

MONTH       IN   OUT
January    210    191
February   200    111
March      132    1         


        

Answer 1

Use:

  SELECT SUM(CASE WHEN p.problem_type = 'IN' THEN 1 ELSE 0 END) AS IN, 
         SUM(CASE WHEN p.problem_type = 'OUT' THEN 1 ELSE 0 END) AS OUT, 
         TO_CHAR(datetime, 'YYYY') AS year,
         TO_CHAR(datetime, 'MM') AS month
    FROM PROBLEM p
   WHERE p.DateTime >= TO_DATE('2010-01-01', 'YYYY-MM-DD') 
     AND p.DateTime < TO_DATE('2010-01-31', 'YYYY-MM-DD') 
GROUP BY TO_CHAR(datetime, 'YYYY'), TO_CHAR(datetime, 'MM')

You could also use:

  SELECT SUM(CASE WHEN p.problem_type = 'IN' THEN 1 ELSE 0 END) AS IN, 
         SUM(CASE WHEN p.problem_type = 'OUT' THEN 1 ELSE 0 END) AS OUT, 
         TO_CHAR(datetime, 'MM-YYYY') AS mon_year
    FROM PROBLEM p
   WHERE p.DateTime >= TO_DATE('2010-01-01', 'YYYY-MM-DD') 
     AND p.DateTime < TO_DATE('2010-01-31', 'YYYY-MM-DD') 
GROUP BY TO_CHAR(datetime, 'MM-YYYY')

Reference:

• TO_CHAR
• TO_DATE

Answer 2

You probably want something like

SELECT SUM( (CASE WHEN problem_type = 'IN' THEN 1 ELSE 0 END) ) in,
       SUM( (CASE WHEN problem_type = 'OUT' THEN 1 ELSE 0 END) ) out,
       EXTRACT( year FROM DateTime ) year,
       EXTRACT( month FROM DateTime ) month
  FROM problem
 WHERE DateTime >= date '2010-01-01'
   AND DateTime < date '2010-01-31'
 GROUP BY EXTRACT( year FROM DateTime ),
          EXTRACT( month FROM DateTime )