Group BY

Justin was recommending a solution to the Chart of Accounts Problem
posted by jamhitz:

MQUOTE>
One has you chart of Accounts
Create table coa (
coa_id serial not null,
parent_id int not null default 0,
doIhaveChildren boolean default false
account_name text null )
primary key(coa_id)

Create Table general_ledger_transactions(
transaction_id serial not null
coad_id integer,
accounting_period integer,
debit numeric(20,10) ,
credit numeric(20,10),
transaction_date datestamp)
primary key (transaction_id)

...

Create table accounting_periods (
accounting_period serial not null,
start_date date,
end_date date,
accounting_period_Open boolean)

</QUOTE>

Would someone please assist me. Why is the following function:...

CREATE OR REPLACE FUNCTION GetChildAccountDebits(PassedAccountID
integer, PassedPeriodID integer) RETURNS NUMERIC AS
$FunctionCode$
DECLARE retval NUMERIC :=0.0;
begin
SELECT Sum(gl_transactions.debit) +
CASE WHEN coa.doIhaveChildren THEN
GetChildAccountDebits(coa.coa_id, PassedPeriodID )
ELSE
0.0
END
INTO retval
FROM gl_transactions, coa
WHERE gl_transactions.coa_id= coa.coa_id
AND coa.parent_id = PassedAccountID
AND gl_transactions.period_id = PassedPeriodID;

RETURN retval;
end;
$FunctionCode$
LANGUAGE 'plpgsql' VOLATILE ;

....failing with an error to the effect that that that
coa.doaIhaveChildren and coa.coa_id must be included in the GROUP BY
clause.... and what is is the recommended course of action.

I have limited Internet access, so forgive me when I raise the same
question 8 days later.

Thanks