how to calculate from each row value in sql - mysql

Question

I have a table named general_ledger from which I need to show dr_amount, cr_amount and the balance between them as running_balance. That's why I have written a query that is given below. But I am getting the result of each query like the balance only of current row. But I need to produce the result with the remaining balance. Suppose First row dr_balance is 20000 and cr_balance is 5000 and remaining balance is 15000. In second row only cr_balance is 5000. Now the result should be 10000 with the deduction but my result is -5000. I have no idea how to fix this. Can anyone please help me on this? I need your help very much. Here is my query given below :
SELECT '' AS cost_center_id
, '' AS cost_center_name
, '' AS office_code
, CONVERT('2013-02-01',DATETIME) AS transaction_date
, '' AS accounts_head_id
, '' AS account_name
, '' AS opposite_accounts_head_id
, '' AS opposite_account_name
, 'Opening Balance' AS particulars
, tempOpeningBalance.dr_amount
, tempOpeningBalance.cr_amount
, '' AS voucher_no
, '' AS vin
FROM (SELECT IFNULL(mcoa.account_code,'1101010101100321') AS account_code
, IFNULL(mcoa.account_name,'Cash') AS account_name
, IFNULL(mcoa.account_type,'ASSET') AS accountType
, CAST(IFNULL(SUM(IFNULL(maingl.dr_balance,0)),0) AS DECIMAL(27,5)) AS dr_amount
, CAST(IFNULL(SUM(IFNULL(maingl.cr_balance,0)),0) AS DECIMAL(27,5)) AS cr_amount
FROM master_chart_of_accounts AS mcoa
INNER JOIN chart_of_accounts AS coa ON (mcoa.id = coa.master_chart_of_accounts_id AND mcoa.id = 80)
LEFT JOIN general_ledger AS maingl ON (coa.id = maingl.accounts_head_id AND coa.account_code='1101010101100321')
INNER JOIN
( SELECT gl.accounts_head_id, MAX(gl.gl_id) AS max_gl_id, gl.office_code, gl.office_type, gl.country_id,gl.cost_center_id
FROM general_ledger AS gl
-- INNER JOIN voucher_info AS vi ON (gl.voucher_info_id = vi.id)
-- WHERE vi.posting_date < '2013-02-01' AND
WHERE gl.transaction_date < '2013-02-01' AND
gl.cost_center_id IN ('BI0000000000000000000001') AND
gl.country_id IN (1) AND
gl.office_code IN ('UG500013') AND
1=1
GROUP BY gl.accounts_head_id, gl.office_code, gl.office_type, gl.country_id,gl.cost_center_id
ORDER BY gl.accounts_head_id
) AS tmpgl
ON ( maingl.office_code = tmpgl.office_code
AND maingl.office_type = tmpgl.office_type
AND maingl.accounts_head_id = tmpgl.accounts_head_id
AND maingl.country_id = tmpgl.country_id
AND maingl.cost_center_id = tmpgl.cost_center_id
AND maingl.gl_id = tmpgl.max_gl_id
)
WHERE mcoa.account_status_id = 1 AND
coa.account_status_id = 1
) AS tempOpeningBalance
UNION
SELECT vi.cost_center_id
, cc.center_name AS cost_center_name
, gl.office_code
, vi.posting_date AS transaction_date
, vd.accounts_head_id
, (SELECT chart_of_accounts.account_name FROM chart_of_accounts WHERE chart_of_accounts.id = vd.accounts_head_id) AS account_name
, vd.opposite_accounts_head_id
, (SELECT chart_of_accounts.account_name FROM chart_of_accounts WHERE chart_of_accounts.id = vd.opposite_accounts_head_id) AS opposite_account_name
, vd.particulars
, gl.dr_amount AS dr_amount -- here to check
, gl.cr_amount AS cr_amount
, vi.voucher_no
, vi.vin
FROM general_ledger AS gl
INNER JOIN voucher_info AS vi
ON (gl.voucher_info_id = vi.id)
INNER JOIN cost_center AS cc
ON (vi.cost_center_id = cc.id)
INNER JOIN voucher_details AS vd
ON (vi.id = vd.voucher_info_id)
INNER JOIN chart_of_accounts AS coa
ON (vd.accounts_head_id = coa.id)
WHERE vi.posting_date BETWEEN '2013-02-01' AND'2013-02-28'
AND vi.voucher_status_id = 3
AND vd.status_id = 1
AND vi.office_code = 'UG500063'
AND coa.account_code='1101010101100321'
AND coa.cost_center_id = 'BI0000000000000000000001'
ORDER BY cost_center_name
, office_code
, transaction_date;

Answer 1

Use a variable like this
SET #running_balance=0;
SELECT dr_amount AS dr_amount
, cr_amount AS cr_amount
, #running_balance := (#running_balance + dr_amount - cr_amount)
FROM general_ledger