火鸟：选择语句中两个字段的乘法的总和

Question

基本上，我需要的是获得两个字段的乘法的总和。

例如： SUM ((field_1 or field_2) * field_3)

但 field_1 或者 field_2 根据第四字段的值选择 field_4

我的桌子：

field_1: Float
field_2: Float
field_3: Float
field_4: Char

简而言之，我需要的就是这样：

SELECT
...
IF field_4 = 'K'
THEN
    SUM( field_1 * field_3 )
ELSE
    SUM( field_2 * field_3 )

我尝试了IF和案例语句，但我无法使其起作用。在这里我的真正查询：

SELECT  
    D.id,
    D.name,
    SUM(CASE WHEN D.sale_unity = 'K' 
        THEN (D.cost_price * CI.quantity_k)
        ELSE (D.cost_price * CI.quantity_u) ) AS total_cost,
    SUM(CASE WHEN D.sale_unity = 'K' 
        THEN (D.sale_price * CI.quantity_k)
        ELSE (D.sale_price * CI.quantity_u) ) AS net
FROM DETAIL D
INNER JOIN VOUCHER AS V ON V.id = D.voucher_id
WHERE V.client_id = 97 AND V.date BETWEEN '06/01/2012' AND '07/01/2012'
GROUP BY D.id, D.name 

Answer 1

我认为您的查询中出了问题是您的案件声明缺少结局。尝试这个：

SELECT  
    D.id,
    D.name,
    SUM(CASE WHEN D.sale_unity = 'K' 
        THEN (D.cost_price * CI.quantity_k)
        ELSE (D.cost_price * CI.quantity_u) END ) AS total_cost,
    SUM(CASE WHEN D.sale_unity = 'K' 
        THEN (D.sale_price * CI.quantity_k)
        ELSE (D.sale_price * CI.quantity_u) END ) AS net
FROM DETAIL D
INNER JOIN VOUCHER AS V ON V.id = D.voucher_id
WHERE V.client_id = 97 AND V.date BETWEEN '06/01/2012' AND '07/01/2012'
GROUP BY D.id, D.name