Question

我有一张如下表所示的表格：

cust_id/frequency
01/null
01/null
02/null
02/null
01/null
03/null
04/null
04/null
03/null

用频率更新表后，它应显示如下

cust_id/frequency
01/3
01/3
02/2
02/2
01/3
03/2
04/2
04/2
03/2

我已经尝试过以下查询，但它只显示我想要的结果，而不是更新表。

select cust_id, count(*) as frequency
from table A 
group by cust_id 
order by count(*) desc

有没有任何查询可以帮助我更新，因为我有10000加上cust_id？

非常感谢你花时间看我的问题。

Answer 1

SQL Server有一个非常好的功能，即CTE（和子查询）可以更新。您可以使用可更新的CTE和窗口函数执行您想要的操作：

with toupdate as (
      select t.*, count(*) over (partition by cust_id) as newfrequency
      from table t
     )
update toupdate
    set frequency = newfrequency;

Answer 2

这样的事情：

UPDATE t1 
SET    t1.frequency = cnt 
FROM   tbl t1 
       JOIN (SELECT cust_id, 
                    Count(1) cnt 
             FROM   tbl 
             GROUP  BY cust_id) t2 
         ON t1.cust_id = t2.cust_id

Answer 3

试试这个 -

DECLARE @temp TABLE
(
    cust_id CHAR(2),
    frequency INT
)

INSERT INTO @temp (cust_id)
VALUES 
    ('01'), ('01'), ('02'), ('02'),( '01'),
    ('03'), ('04'), ('04'), ('03')

;WITH cte AS 
(
    SELECT cust_id, cnt = COUNT(1) 
    FROM @temp
    GROUP BY cust_id
)
UPDATE @temp
SET frequency = cnt
FROM cte
WHERE cte.cust_id = [@temp].cust_id

SELECT * FROM @temp

输出 -

cust_id frequency
------- -----------
01      3
01      3
02      2
02      2
01      3
03      2
04      2
04      2
03      2

按频率更新客户ID

3 个答案: