mysql - 使用 count 查询不存在的地方

Question

我正在从我拥有的 2 个表中随机获取客户，

customer
========
id
first_name
surname
country

call_log
====
id
customer_id #FK
create_by
create_datetime
status (status for No answer is 7)

到目前为止，我需要排除通话记录中出现 2 次无应答状态的客户。我已经尝试过了

SELECT
    customer.id, 
    customer.first_name,
    customer.country
FROM
    customer
WHERE
    NOT EXISTS
    (
        SELECT 1 #I dont know what I should do here
        FROM 
            call_log
        WHERE
            call_log.customer_id = customer.id AND
            call_log.status = 7 AND #no answer
            call_log.create_datetime BETWEEN '2015-10-06 00:00:00' AND '2015-10-06 23:59:59'
    )

非常感谢任何帮助。谢谢。

Answer 1

让子选择返回“否”的数量。

SELECT
    customer.id, 
    customer.first_name,
    customer.country
FROM
    customer
WHERE (SELECT count(*)
       FROM call_log
       WHERE call_log.customer_id = customer.id AND
             call_log.status = 7 AND #no answer
             call_log.create_datetime BETWEEN '2015-10-06 00:00:00'
                                          AND '2015-10-06 23:59:59') < 2