CASE語句的WHERE子句

Question

我試圖獲取在那裏我的WHERE子句中使用CASE條件從表中的數據，目前我使用下面的查詢： -

SELECT count(enq_id) AS total, sum(purchase_amount) AS purchase 
FROM temp_stock 
WHERE purchase_date <> '0000-00-00' 
AND purchase_date < '2012-08-01' 
AND (

STATUS = 'Sold' 
OR STATUS = 'In Stock' 
OR STATUS = 'Ref' 
) 
AND CASE WHEN (

STATUS = 'Sold' 
) 
THEN delivery_date >= '2012-08-01' 
END 

但它返回0對於total和NULL對於purchase。

Answer 1

從your comment。

我想用Case語句，可以ü請澄清我有關情況statament在where子句

您可以使用CASE聲明WHERE這樣的：

SELECT count(enq_id) AS total, sum(purchase_amount) AS purchase 
FROM temp_stock 
WHERE purchase_date <> '0000-00-00' 
AND purchase_date < '2012-08-01' 
AND ( STATUS = 'Sold' 
     OR STATUS = 'In Stock' 
     OR STATUS = 'Ref') 
AND CASE STATUS 
     WHEN 'Sold' 
     THEN delivery_date >= '2012-08-01' 
     ELSE 1=1 
    END 

這裏，您需要使用ELSE 1=1。否則你不會得到理想的結果。有關更多解釋，請參閱this SQLFiddle

Answer 2

我不認爲CASE可以這樣工作。你想要的是一個稍微複雜的表達式作爲你的WHERE子句。可能是這樣的：

SELECT count(enq_id) AS total, sum(purchase_amount) AS purchase 
FROM temp_stock 
WHERE purchase_date <> '0000-00-00' 
    AND purchase_date < '2012-08-01' 
    AND (
    (STATUS = 'Sold' AND delivery_date >= '2012-08-01') 
    OR STATUS = 'In Stock' 
    OR STATUS = 'Ref' 
)