创建新的 sql 列以获得新值

Question

我有这笔交易 table 我如何查询一个人是否是新客户、回头客、回头客、非会员。例如，当 sequence = 1 时，id 1 是一个新客户，他们只能在购买类型（成员）后成为 member/returning-member 例如 id 1 和 sequence 4 是返回的非成员，因为这是他们第一次购买会员。在交易 seq 5 之后，他们现在是回头客

虽然 id 2 从未购买过会员，因此第一个序列将是新客户，但其他人将是非会员回头客，直到他们购买会员。

问题

id	Type	Date	Sequence
1	Member	2021-02-24	4
1	product	2021-01-03	2
2	service	2022-04-21	5
1	product	2021-02-01	3
2	service	2022-02-16	3
1	Member	2022-02-03	6
1	Service	2021-10-23	5
2	product	2022-01-03	2
1	service	2020-12-16	1
2	product	2022-03-30	4
2	service	2021-12-01	1
1	Member	2022-04-03	7

结果

id	Type	Date	Sequence	New column
1	Member	2021-02-24	4	Returning-Non-member
1	product	2021-01-03	2	Returning-Non-member
2	service	2022-04-21	5	Returning-Non-member
1	product	2021-02-01	3	Returning-Non-Member
2	service	2022-02-16	3	Returning-Non-member
1	Member	2022-02-03	6	Returning-Member
1	Service	2021-10-23	5	Returning-Member
2	product	2022-01-03	2	Returning-Non-Member
1	service	2020-12-16	1	New Client
2	product	2022-03-30	4	Returning-Non-Member
2	service	2021-12-01	1	New Client
1	Member	2022-04-03	7	Returning-Member

Answer 1

您可以使用额外的子查询以非常直接的方式完成此操作，但就性能而言，这不是最佳方式。

SELECT
    *,
    CASE 
        WHEN t.Sequence = 1 THEN 'New Client'
        WHEN 
            EXISTS (
                SELECT * 
                    FROM YourTable AS th 
                    WHERE 
                        th.Date < t.Date 
                        AND th.Id = t.Id 
                        AND th.Type ILIKE 'Member'
            ) THEN 'Returning-Member' 
        ELSE 'Returning-Non-Member'
    END AS Membership
    FROM YourTable AS t

创建新的 sql 列以获得新值

create new sql column to get new value

postgresql

amazon-redshift