Question

我正在尝试在下面的查询中添加表t4的计数，而不限制结果。类似的东西：

 COUNT(t4.offer_to_purchase_id) AS count

但这会将结果限制为仅显示在t4中的那些服务，尽管有左连接

$sql = "SELECT s.*, q.categories, t4.*, payments.*, quotes.*
      FROM services s

      LEFT JOIN 
       (
      SELECT sc.service_id, GROUP_CONCAT(c.name) categories
        FROM services_categories sc JOIN categories c 
          ON sc.cat_id= c.cat_id
       GROUP BY sc.service_id
       ) q ON s.service_id = q.service_id

      LEFT JOIN offers_to_purchase t4
      ON s.service_id = t4.service_id 
      LEFT JOIN quotes ON quotes.service_id = s.service_id
      LEFT JOIN payments ON payments.service_id = s.service_id
      WHERE s.user_id = $user_id";

我怎样才能做到这一点？

Answer 1

它应该工作（因为它将计算非空值），但不确定如何对记录进行分组以获取它，看到你似乎正在返回该表中的所有记录。

如果你想要一个可以用于所有行的计数，同时从t4带回行，你可以这样做： -

$sql = "SELECT s.*, q.categories, t4.*, payments.*, quotes.*, t4_2.id_count
      FROM services s

      LEFT JOIN 
       (
      SELECT sc.service_id, GROUP_CONCAT(c.name) categories
        FROM services_categories sc JOIN categories c 
          ON sc.cat_id= c.cat_id
       GROUP BY sc.service_id
       ) q ON s.service_id = q.service_id

      LEFT JOIN offers_to_purchase t4
      ON s.service_id = t4.service_id 
      LEFT OUTER JOIN 
      (
        SELECT service_id, COUNT(offer_to_purchase_id) AS id_count FROM offers_to_purchase GROUP BY service_id
      ) t4_2
      ON s.service_id = t4_2.service_id
      LEFT JOIN quotes ON quotes.service_id = s.service_id
      LEFT JOIN payments ON payments.service_id = s.service_id
      WHERE s.user_id = $user_id";

MySQL计算左连接表中的行数

1 个答案: