Question

由于我是SQL的新手，我不确定如何表达我的问题。这不应该太难。这是场景。

我有3张桌子：

客户

id, 
contact

subscribers_from_x

customer_id
 subscriber_name

subscribers_from_y

customer_id,
subscriber_name

这是一个问题：

现在，我想选择

customer.id

来自subscriber.id的次数/次数发生在subscriber_from_x

来自subscriber.id的次数/次数发生在subscriber_from_y

来自这3个表

我试过了GROUP_BY COUNT(*)但没有弄明白。感谢

Answer 1

我可能会使用两个单独的子查询，这些子查询按订阅者聚合x和y表的计数：

SELECT t1.id,
       t1.contact,
       COALESCE(t2.x_count, 0) AS subscribers_from_x,
       COALESCE(t3.y_count, 0) AS subscribers_from_y
FROM customers t1
LEFT JOIN
(
    SELECT customer_id, COUNT(*) AS x_count
    FROM subscribers_from_x
    GROUP BY customer_id
) t2
    ON t1.id = t2.customer_id
LEFT JOIN
(
    SELECT customer_id, COUNT(*) AS y_count
    FROM subscribers_from_y
    GROUP BY customer_id
) t3
    ON t1.id = t3.customer_id

Answer 2

SELECT DISTINCT(users.id),count(x.customer_id) 'X count',count(y.customer_id) 'Y Count'
       FROM customers 
          LEFT  JOIN subscribers_from_x x ON customers.id = x.customer_id
          LEFT  JOIN subscribers_from_y y ON customers.id = y.customerid
        GROUP BY customers.id,subscribers_from_x.pk_col -- primary key col of subscribers_from_x

它将为您提供所需的输出

来自多个表的SQL语句组数据

2 个答案: