如何计算列中的出现次数，同时包含具有 SQL 的唯一值的另一列？

Question

我有 table 个客户：

id	order
0	25
1	25
2	23
3	24
4	25

我想查询所有客户，以及一个计算相同订单号的客户数量的附加列：

id	order	count
0	25	3
1	25	3
2	21	1
3	25	3
4	22	1

我试过这个语法

SELECT A.id, A.0rder, B.cnt
  FROM Customers  A
  INNER JOIN (
    SELECT Order, count(Order) as cnt
      FROM Customers 
      GROUP BY Order
  ) B ON A.Order = B.Order

和运行进入这个错误。 'Error saving the Query field.Old style JOIN (ANSI JOINs) syntax is not allowed. Please use standard syntax.'

Answer 1

您查询的问题是您名为 order 的列也是一个关键字，例如 ORDER BY。您可以使用 table 别名解决此问题，如下所示：

SELECT 
    A.id, A.order, 
    B.cnt 
FROM 
    Customers A 
INNER JOIN (
  SELECT b.Order, count(b.Order) as cnt 
  FROM Customers b GROUP BY b.Order
) B ON A.Order = B.Order;

id	order	cnt
0	25	3
1	25	3
2	23	1
3	24	1
4	25	3

View on DB Fiddle

您也可以将 window 函数 COUNT 与订单列上的分区一起使用，或使用相关查询来实现此目的。这两种方法都包含在下面。

查询 #1 - Window 函数

SELECT
    t1.*,
    COUNT(1) OVER (PARTITION BY t1.order) as count
FROM
    my_table t1
ORDER BY 
    t1.id;

id	order	count
0	25	3
1	25	3
2	23	1
3	24	1
4	25	3

查询 #2

SELECT
    t1.*,
    (
        SELECT COUNT(1) FROM my_table t2 WHERE t2.order=t1.order
    ) as count
FROM
    my_table t1
ORDER BY 
    t1.id;

id	order	count
0	25	3
1	25	3
2	23	1
3	24	1
4	25	3

View Demo on DB Fiddle

让我知道这是否适合你。

如何计算列中的出现次数，同时包含具有 SQL 的唯一值的另一列？

How to Count Occurrences in a Column while including another column with unique values with SQL?

sql

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