selecting the month day and year from a transaction table
You will want to use the DATE_FORMAT function in MySQL to format the date for each query.

-- query 1
select date_format(date, '%m-%d') `m-d`,
  sum(amount) Total
from mytable
group by date_format(date, '%m-%d');


See SQL Fiddle with Demo. Gives a result:

|   M-D | TOTAL |
-----------------
| 04-08 |    50 |
| 05-01 |   200 |
| 05-03 |   400 |

-- query 2
select date_format(date, '%Y-%m') `Y-m`,
  sum(amount) Total
from mytable
group by date_format(date, '%Y-%m');


See SQL Fiddle with Demo. Gives the result:

|     Y-M | TOTAL |
-------------------
| 2013-04 |    50 |
| 2013-05 |   600 |