Sql中Case用法与Oracle中Case和Decode用法

Sql中Case用法：

select
a.customer_id,
a.currency_id,
b.balance,
isnull(sum(-c.amount),0) credit_amount,
isnull(sum(d.amount),0) debit_amount,
isnull(sum(case when a.invoice_date < 0 then a.amount end),0) amount0,
isnull(sum(case when a.invoice_date BETWEEN   0 and 30 then a.amount end),0) amount30,
isnull(sum(case when a.invoice_date BETWEEN   31 and 60 then a.amount end),0) amount60,
isnull(sum(case when a.invoice_date BETWEEN   61 and 90 then a.amount end),0) amount90
from
(select
customer_id,currency_id,
datediff(day,getdate(),
invoice_date)+payment_terms invoice_date,
amount_total-amount_settled amount
from customer_invoice) a

join customer_current_account b
on a.customer_id = b.customer_id
and a.currency_id= b.currency_id

left join customer_credit_note c
on a.customer_id = c.customer_id
and a.currency_id = c.currency_id

left join customer_debit_note d
on a.customer_id = d.customer_id
and a.currency_id = d.currency_id

group by a.customer_id,a.currency_id,b.balance

Oracle中的Case与Sql差不多：

   SELECT LogID,UserID,LogTime,Url,Description,(

　　case

　　when OperateType = 0

　　then '新增'

　　when OperateType＝1

　　then '修改'

　　else '删除'

　　end )    OperationName

FROM LOG

   也可以用Oracle中的 Decode 函数

       ·含义解释:

　　decode(条件,值1,翻译值1,值2,翻译值2,...值n,翻译值n,缺省值)

        SELECT LogID,UserID,LogTime,Url,Description,

　　decode(OperateType,0,'新增',1,'修改','删除') OperationName

　　FROM LOG