Question

有没有办法计算已离开连接的数据透视表，然后再次在数据透视表上运行where子句以过滤掉不需要的其余部分？

以下是我到目前为止：

SELECT *
FROM 
      (
          SELECT COUNT(user_id) as Count
          FROM group_buys
      ) GroupBuy
      LEFT JOIN group_buy_users GroupBuysUser
          ON GroupBuysUser.group_buy_id = GroupBuy.id
WHERE GroupBuysUser.user_id = {$this->Auth->user('id')}

我找到了解决方案：

SELECT *
        FROM group_buys GroupBuy
        LEFT JOIN group_buy_users GroupBuysUser
        ON GroupBuysUser.group_buy_id = GroupBuy.id
        LEFT JOIN (
            SELECT group_buy_id, COUNT(user_id) as Count
            FROM group_buy_users
            GROUP BY group_buy_id
        ) GroupBuysUserCount
        ON GroupBuysUserCount.group_buy_id = GroupBuy.id
        LEFT JOIN group_buy_merchant_offers GroupBuysMerchantOffer
        ON GroupBuysMerchantOffer.group_buy_id = GroupBuy.id
        WHERE GroupBuysUser.user_id = {$this->Auth->user('id')}
        GROUP BY GroupBuy.id
        HAVING GroupBuy.expiry_date > NOW()
        ORDER BY GroupBuysMerchantOffer.bid_price ASC

基本上我只需要做一个LEFT JOIN一个虚拟表，它已经在其id上使用group buy计数，然后user_id属于user的子句然后再在Groupbuy.id上进行分组以消除重复。我添加了到期，因为我必须删除所有过期的旧组件，但是这会从group_buy_users表中添加组用户的数量，然后再添加group_buy_users表，因此我可以检索其他详细信息。

Mysql使用count然后条件加入数据透视表

0 个答案: