SQL 我如何根据条件对记录进行分组？

Question

我正在尝试查找总共拥有至少 4 个帐户且至少有 1 个帐户在过去 6 个月内开设的所有客户。

到目前为止，我能够获得客户和总帐户数，但我不确定如何为过去 6 个月内开设的新帐户数添加一列。

SELECT CustomerID
       ,COUNT(AccountID) as 'Total Accounts'
FROM Customer
GROUP BY CustomerID
HAVING COUNT(AccountID) >= 3`

这是我的表格：

和

我的最终结果应该是这样的。到目前为止，我有 CustomerID 和 Total Accounts。

CustomerID | Total Accounts | New Accounts |
-----------+----------------+------------- +
    Ben    |       3        |      1       |

编辑：我将在其中导入此查询的程序不允许 case 语句。

Answer 1

此查询将为您提供帐户总数和新帐户数。

SELECT C.CustomerID,
       COUNT(C.AccountID) as Total_Acc,
       SUM(CASE WHEN DATEADD(MONTH,-6,GETDATE()) <= A.StarDate) THEN 1 ELSE 0 END) as New_Acct
FROM Customer C
LEFT JOIN Account A ON C.AccountID = A.AccountID
GROUP BY CustomerID

然后您可以在子查询中使用它来查找您想要的内容

例如

SELECT * 
FROM (
  SELECT C.CustomerID,
       COUNT(C.AccountID) as Total_Acc,
       SUM(CASE WHEN DATEADD(MONTH,-6,GETDATE()) <= A.StarDate) THEN 1 ELSE 0 END) as New_Acct
  FROM Customer C
  LEFT JOIN Account A ON C.AccountID = A.AccountID
  GROUP BY CustomerID
) SUB
WHERE Total_Acc >= 4 and New_Acct >= 1

Answer 2

Count，像大多数聚合函数一样，忽略 nulls。我将通过连接两个表并使用 case 表达式来使用此属性仅 return 新帐户：

SELECT   CustomerId, 
         COUNT(*) AS TotalAccounts,
         COUNT(CASE WHEN DATEDIFF(MONTH, StartDate, GETDATE()) <= 6 THEN 1 END) 
           AS NewAccounts
FROM     Customer c
JOIN     Accounts a ON c.AccountId = a.AccountId
GROUP BY CustomerId
HAVING   COUNT(*) >= 4 AND
         COUNT(CASE WHEN DATEDIFF(MONTH, StartDate, GETDATE()) <= 6 THEN 1 END) > 0

Answer 3

The program I'll be importing this query in doesn't allow case statements.

对于您的既定目标，即寻找至少拥有 4 个帐户且至少有 1 个帐户在过去 6 个月内开设的客户，您无论如何都不需要最近帐户的数量。获取最新的开户日期并查看是否在最近 6 个月内就足够了。

SELECT c.CustomerId
FROM   Customer c
       JOIN Accounts a
         ON c.AccountId = a.AccountId
GROUP  BY c.CustomerId
HAVING COUNT(*) >= 4
       AND MAX(a.StartDate) >= DATEADD(MONTH, -6, GETDATE())

Answer 4

您可以离开加入新帐户。在连接条件中包含 startdate 的过滤器。对于不满足该条件的帐户，不会加入来自 account 的记录。因此帐户 ID 对他们来说是空的，不会被计算在内。

SELECT c.customerid,
       count(c.accountid) "Total Accounts",
       count(a.accountid) "New Accounts"
       FROM customer c
            LEFT JOIN account a
                      ON a.accountid = c.accountid
                         AND a.startdate >= dateadd(month, -6, getdate())
       GROUP BY c.customerid
       HAVING count(c.accountid) >= 4
              AND count(a.accountid) >= 1;

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