Postgresql Union

union_by_categories.sql

Tables to Union Join
  Expenses
  Bills
  Income

On 
  Categories

I have 28 categories that I would like to sum all transaction amounts for by a given time period.
When I run each select statement for each table by itself, I get the 28 rows per each category.
When I use the UNION for all three tables, I get more than 28 records.
It includes the 'duplicate' category when there is a amount for that category.
I know that UNION will not include duplicates...
I need to rewrite this query to return expenses, bills and income summed against each category.
I would prefer to do this in the database than using some reduce on the client.

I have tried several re-writes, but any suggestions on how to write a query would be helpful.
Still not seeing the solution...


SELECT cat.name AS category, SUM(ex.amount) AS weekly_total, trx.id AS type
FROM categories cat
FULL OUTER JOIN expenses ex ON (cat.id = ex.categorytype)
AND date_trunc('month', ex.trxdate) = date_trunc('month', current_date)
INNER JOIN transaction_type trx ON (cat.transactiontype = trx.id)
GROUP BY cat.name, trx.id
UNION
SELECT cat.name AS category, SUM(bl.amount) AS weekly_total, trx.id AS type
FROM categories cat
FULL OUTER JOIN bills bl ON (cat.id = bl.categorytype)
AND date_trunc('month', bl.paiddate) = date_trunc('month', current_date)
INNER JOIN transaction_type trx ON (cat.transactiontype = trx.id)
GROUP BY cat.name, trx.id
UNION
SELECT cat.name AS category, SUM(inc.netamount) AS weekly_total, trx.id AS type
FROM categories cat
FULL OUTER JOIN income inc ON (cat.id = inc.categorytype)
AND date_trunc('month', inc.payday) = date_trunc('month', current_date)
INNER JOIN transaction_type trx ON (cat.transactiontype = trx.id)
GROUP BY cat.name, trx.id;



Returns..

Cateogry Amount TrxType
Alcohol		2
Alcohol	  7.7	  2
Bill Payment		2
Bill Payment	6.5	2
Car Fuel		2
Car Fuel	35.2	2
Car Insurance Bill	131.96	1
Car Insurance Bill		1
Card Payment		4
Cash		7
Cash Withdrawal		4
Checking		7
Clothes Expense		4
Credit		7
Dine Out		4
Dine Out	92.33	4
Electric Bill		2
Gas Bill		2
Gift		4
Groceries		2
Groceries	181.81	2
House Expense		4
House Expense	5.25	4
Internet Bill	62.52	1
Internet Bill		1
Loan		6
Loan Payment	234.9	4
Loan Payment		4
Miscellaneous		4
Paycheck		5
Paycheck	1434.37	5
Personal Expense		4
Phone Bill		1
Rent	950	1
Rent		1
Retirement		7
Saving		7
Tech Expense	30.22	4
Tech Expense		4
Water Bill		2