簡單的SQL查詢與多個表

Question

我試圖寫一個簡單的查詢，但輸出是不正確的：

Herer我的代碼：

SELECT oc_order_product.order_id AS ordernumber, oc_order_product.quantity, 
     oc_order_product.model, oc_order_product.name, 
     oc_order.shipping_company, oc_order.shipping_firstname, 
     oc_order.shipping_lastname, oc_order.shipping_city, oc_product.location 
FROM oc_order_product, 
    oc_order, 
    oc_product 
WHERE oc_order.order_id = oc_order_product.order_id 
    AND oc_order.order_status_id = 1 
    AND oc_product.location = 1 
ORDER BY ordernumber, oc_order_product.model 

輸出是與所有產品的列表oc_order.order_status_id = 1，但第二個AND（oc_product.location = 1）未應用。哪裏不對？我不使用JOIN，因爲我不太瞭解它。

Answer 1

現在用現代的，明確的JOIN：

SELECT oc_order_product.order_id AS ordernumber, oc_order_product.quantity, 
     oc_order_product.model, oc_order_product.name, 
     oc_order.shipping_company, oc_order.shipping_firstname, 
     oc_order.shipping_lastname, oc_order.shipping_city, oc_product.location 
FROM oc_order_product 
    INNER JOIN oc_order ON oc_order.order_id = oc_order_product.order_id 
    INNER JOIN oc_product ON oc_product.id = oc_order_product.product_id 
WHERE oc_order.order_status_id = 1 
    AND oc_product.location = 1 
ORDER BY ordernumber, oc_order_product.model 

，去年加入

INNER JOIN oc_product ON oc_product.id = oc_order_product.product_id 

只是一個猜測，因爲我不知道該用哪些列！

Answer 2

jarlh正在猜測oc_product.id = oc_order_product.product_id。

我要去猜測，你的數據元素名稱始終如一和獨特的整個架構命名，因此建議您使用超現代NATURAL JOIN：

SELECT order_id AS ordernumber, quantity, 
     model, name, shipping_company, shipping_firstname, 
     shipping_lastname, shipping_city, location 
    FROM oc_order_product 
     NATURAL JOIN oc_order 
     NATURAL JOIN oc_product 
    WHERE order_status_id = 1 
     AND location = 1 
    ORDER 
     BY ordernumber, model; 

...不就行了投注農場，雖然。