php - 使用多个表在 mysql 中进行多个联合和联接

Question

我在 mysql 查询中创建了 UNION。这对我来说效果很好。

此查询的主要目的是从多个表中获取通知的数据。

这需要 0.0009 秒 时间来执行。数据较少。

任何sql专家可以帮助我改进这个sql查询或者指导我这个sql查询吗？

我不太擅长mysql

  SELECT
        HM_notification.product_id,
        HM_products.slug,
        HM_notification.action_type,
        HM_notification.url,
        HM_notification.read_date
        FROM `HM_notification` 
            JOIN HM_customers ON HM_customers.id = HM_notification.added_by 
            JOIN HM_products ON HM_products.id = HM_notification.product_id 
            JOIN HM_reviews ON HM_reviews.product_id = HM_notification.product_id 
            WHERE HM_products.user_id=34 AND HM_notification.added_by != 34 AND action_type = 'reviews'

    UNION        

  SELECT 
        HM_notification.product_id,
        HM_products.slug,
        HM_notification.action_type,
        HM_notification.url,
        HM_notification.read_date
        FROM `HM_notification` 
            JOIN HM_customers ON HM_customers.id = HM_notification.added_by 
            JOIN HM_bid ON HM_bid.product_id = HM_notification.product_id 
            JOIN HM_products ON HM_products.id = HM_notification.product_id 
            WHERE HM_products.user_id=34 AND HM_notification.added_by != 34  AND action_type = 'newbid' OR action_type = 'editbid'

    UNION        

    SELECT 
        HM_notification.product_id,
        HM_products.slug,
        HM_notification.action_type,
        HM_notification.url,
        HM_notification.read_date
        FROM `HM_notification` 
            JOIN HM_customers ON HM_customers.id = HM_notification.added_by 
            JOIN HM_products ON HM_products.id = HM_notification.product_id 
            JOIN HM_order_items ON HM_order_items.product_id = HM_notification.product_id 
            WHERE HM_products.user_id=34 AND HM_notification.added_by != 34 AND (action_type = 'order_pending' OR action_type = 'processing' OR action_type = 'onhold' OR action_type = 'unhold' OR action_type = 'receive' OR action_type = 'addshipment' OR action_type = 'editshipment' OR action_type = 'newcomment' OR action_type = 'addshipmentcomment')

    UNION        

  SELECT 
        HM_notification.product_id,
        HM_products.slug,
        HM_notification.action_type,
        HM_notification.url,
        HM_notification.read_date
        FROM `HM_notification` 
            JOIN HM_customers ON HM_customers.id = HM_notification.added_by 
            JOIN HM_products ON HM_products.id = HM_notification.product_id 
            JOIN HM_conversation ON HM_conversation.pid = HM_notification.product_id 
            WHERE HM_products.user_id=34 AND HM_notification.added_by != 34 AND (HM_conversation.user_one != 34 || HM_conversation.user_two != 34) AND action_type = 'conversation'

这是一个简单的 SQL 查询，用于获取带有产品 ID 的特定 url。

Answer 1

因为我还没有看到你的表，所以我现在的想法是，如果可能的话，你最好使用“NATURAL JOIN”而不是“JOIN”，并将条件放在查询的“WHERE”部分。因为前者更快、更明智......

希望有帮助...