我如何Substract同一列的两个不同的单元格

Question

如果有相同的组名称，我想减去Open Balance Cells，我的意思是Balance_type 0是借方，1是贷方   我期待结果是具有相同组名

的未结余额的借方贷方

我的真实SQL语句就是这个：

SELECT 
    tblLedgerGroup.group_type, tblLedgerGroup.group_name, tblLedgerGroup_1.group_name AS [Group Name]
    , SUM(tblLedgerNames.op_balance) AS [Open Balance]
    , tblLedgerNames.balance_type
    , SUM(tblCashLedger.debit) AS [Total Debit]
    , SUM(tblCashLedger.credit) AS [Total Credit]
FROM 
     tblLedgerGroup 
LEFT OUTER JOIN
    tblLedgerGroup AS tblLedgerGroup_1 ON tblLedgerGroup.group_id = tblLedgerGroup_1.parent_group_id 
LEFT OUTER JOIN
    tblLedgerNames ON tblLedgerGroup_1.group_id = tblLedgerNames.group_id
LEFT OUTER JOIN
    tblCashLedger ON tblLedgerNames.ledger_id = tblCashLedger.account_id 
GROUP BY 
    tblLedgerGroup.group_type, tblLedgerGroup.group_name, tblLedgerGroup_1.group_name, tblLedgerNames.balance_type