Performing Comparisons in Star Schema by Year and Department

Greetings,
I have this Schema

CREATE TABLE `PAY_FACT` (
    `PAYNO` int(11) default NULL,
    `ORGN_CODE` varchar(6) default NULL,
    `POSN` varchar(6) default NULL,
    `EARN_CODE` varchar(3) default NULL,
    `HRS` double default NULL,
    `RATE` double default NULL,
    `AMT` double default NULL,
    `date_id` bigint(20) default NULL,
    KEY `EARN` (`EARN_CODE`),
    KEY `POSN` (`POSN`),
    KEY `ORGN` (`ORGN_CODE`)
)  ENGINE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `dept_ref` (
    `CODE` varchar(6) default NULL,
    `TITLE` varchar(35) default NULL,
    KEY `CODE` (`CODE`)
)  ENGINE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `earn_ref` (
    `CODE` varchar(3) default NULL,
    `SHORT_DESC` varchar(8) default NULL,
    `LONG_DESC` varchar(30) default NULL,
    KEY `CODE` (`CODE`),
    KEY `SHORT` (`CODE` , `SHORT_DESC`),
    KEY `LONG` (`CODE` , `LONG_DESC`)
)  ENGINE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `date_ref` (
  `date_id` bigint(20) NOT NULL,
  `date` date NOT NULL,
  `timestamp` bigint(20) NOT NULL,
  `weekend` char(10) NOT NULL default 'Weekday',
  `day_of_week` char(10) NOT NULL,
  `month` int(11) NOT NULL,
  `month_name` char(10) NOT NULL,
  `month_day` int(11) NOT NULL,
  `year` int(11) NOT NULL,
  `FY` int(11) NOT NULL,
  `FQ` int(11) NOT NULL,
  `week_starting_monday` char(2) NOT NULL,
  PRIMARY KEY  (`date_id`),
  UNIQUE KEY `date` (`date`),
  KEY `year_week` (`year`,`week_starting_monday`),
  KEY `month_day` (`month`,`month_day`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

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I am required to have a SUM of the AMT field in the PAY_FACT table by department and Earning Code.
Department Titles: PAY_FACT.ORGN_CODE = dept_ref.TITLE
Earning Codes: PAY_FACT.EARN_CODE = earn_ref.CODE

This sum is to be between two dates.  In addition, I need five other AMT fields for the Years Prior.
The output I am trying to achieve is this:

DEPT                 EARN_TYPE             CFY_AMT            YR1_AMT   YR2_AMT  YR3_AMT YR4_AMT YR5_AMT
Supply                BiWeekly_PAY            5000                  4500         4200           3800         4500        2600
Admin                Overtime_PAY            1200                 1140           1254           1000           454        1560

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My biggest problem is getting the YR1 through YR5.
They are the dates equal back 1 year, 2 years, 3years, 4 years, and 5 years.
NULLS need to be converted to 0's
How do I go about this?
Thanks