GL_Balance Query

SELECT
gb.set_of_books_id,
(nvl(gb.begin_balance_dr,0) -nvl(gb.begin_balance_cr,0) + nvl(gb.period_net_dr,0) -nvl(gb.period_net_cr,0)) actual_balance,
(nvl(gb.begin_balance_dr_beq,0) -nvl(gb.begin_balance_cr_beq,0) +nvl(gb.period_net_dr_beq,0) -nvl(gb.period_net_cr_beq,0)) actual_balance_accounted,
(nvl(gb.begin_balance_dr,0) -nvl(gb.begin_balance_cr,0)) actual_begin_balance
--Sum (gb.begin_balance_dr) opening_balance_dr,
--Sum (gb.begin_balance_cr) opening_balance_cr
FROM
gl_balances gb,
GL_PERIOD_STATUSES GL,
gl_code_combinations gcc
WHERE
gb.set_of_books_id=gl.set_of_books_id AND
gb.code_combination_id=gcc.code_combination_id and
gl.application_id=101 and
gb.set_of_books_id =8 AND
gb.period_year=2010 AND
gb.period_num=3
--GROUP BY
--gb.set_of_books_id,
--gb.period_year,
--gb.period_num
--ORDER BY
--1