sql - 对 null 的算术运算

Question

LedgerId    AccountId   EntryType   Debit       Credit      
2               2           D       50000.00    NULL        
3               2           D       10000.00    NULL        
4               2           C       NULL        25000.00    
6               2           C       NULL        10000.00    
7               2           D       89000.00    NULL        
8               2           D       89000.00    NULL        
10              3           D       715871.00   NULL        

以下查询计算 Balance :

Select Accounts.ID [AccountID],Name,AccountType [AccountType], SUM(Debit) - SUM(Credit) [Balance] FROM Accounts 
    join Dealers on Accounts.DealerId = Dealers.ID 
    join Ledger on Accounts.ID = Ledger.AccountId
    GROUP BY Accounts.ID, Name, AccountType

它返回:

AccountID   Name    AccountType     Balance
2           Mateen  P               203000.00
3           Shery   P               NULL

预期输出:

AccountID   Name    AccountType     Balance
2           Mateen  P               203000.00
3           Shery   P               715871.00

Balance如果帐户 3 为空，则返回 null当涉及到从 null 中减去任何内容时.

例如:

select 5 - NULL

返回 NULL .

问题:现在，我怎样才能获得 Balance而不是 NULL ?

Answer 1

您可以使用 coalesce :

coalesce(sum(Debit), 0) - coalesce(sum(Credit), 0)