用内连接 sql 查询计数

Question

大家好，我们有两个表“订阅信息，激活信息” 两个表的结构是这样的

订阅信息表

   cert_id (int, PK)
   customer_email(string)
   subscription_key(string)
   activated_on (datetime)

激活信息表：

    cert_id (int)
    activationcode(string)
    subscription_key(string , FK)
    activated_ts(datetime)

如果 Subscriptioninfo 条目具有相同年份和客户电子邮件 ID（这很好），则以下查询将计数为“one”

SELECT COUNT(*) FROM Subscriptioninfo WITH (NOLOCK)
WHERE year(activated_On) = year(getdate()) AND customer_email =@CustomerEmail

我们有一个 sp 会将数据插入到两个表中（即 Subscriptioninfo 的一个条目，而activationinfo 的四个条目

如果订阅信息有一个条目，激活信息有两个条目，我需要将计数返回为“0”

如果订阅信息有一个条目，而激活信息有四个条目，我需要将计数返回为“1”..

有人可以帮忙解决这个问题吗？我怎么能用 join 子句得到这个计数。。

提前非常感谢...

尝试使用此查询，但它给出了activationinfo条目计数（即）4 而不是 1

 SELECT COUNT(*) FROM subscriptioninfo csi join activationinfo aci on csi.subscription_key = aci.subscription_key
 WHERE year(Activated_On)  = year(getdate()) AND customer_email = 'xxx@cc.com' group by csi.subscription_key

Answer 1

使用CASE 语句

SELECT CASE WHEN COUNT(*) = 4 THEN 1
            WHEN COUNT(*) < 4 THEN 0
       END CountResults
FROM subscriptioninfo csi 
join activationinfo aci on csi.subscription_key = aci.subscription_key
WHERE year(Activated_On)  = year(getdate()) AND customer_email = 'xxx@cc.com' group by csi.subscription_key

Answer 2

我只是想与众不同，可能性能更好，

;WITH CTE
AS (
    SELECT *
        ,row_number() OVER (
            ORDER BY cert_id
            ) rn
    FROM @activationinfo A
    )
SELECT *
    ,1 AS CountResult
FROM @Subscriptioninfo S
WHERE EXISTS (
        SELECT cert_id
        FROM CTE A
        WHERE s.cert_id = a.cert_id
            AND rn = 4
        )

UNION ALL

SELECT *
    ,0 AS CountResult
FROM @Subscriptioninfo S
WHERE EXISTS (
        SELECT cert_id
        FROM CTE A
        WHERE s.cert_id = a.cert_id
            AND rn < 4
        )