加入3tables； select 来自第三 table 行，其中包含最新日期的特定字符串

Question

我有 3 个 table，其中我需要从第 3 个 table 搜索这个特定字符串 '%sell back%' 并获取 latest 条目来自 table，3 个 table 如下：

Table#1：客户

|---------------|---------------|
|  Customer ID  | CustomerName  |
|---------------|---------------|
|    1234       | Johnathan     |
---------------------------------

Table#2：问题

|---------------|---------------|----------------------|---------------|
|  Problem ID   | CustomerID    | Problem Description  | Date Reported |
|---------------|---------------|----------------------|---------------|
|    3203494    | 1234          | Needs Appointment    | 2019-08-01    |
------------------------------------------------------------------------
|    3178766    | 1234          | Sell Back Customer   | 2019-08-12    |
------------------------------------------------------------------------

Table#3：问题事件

|---------------|---------------|----------------------|---------------|
|ProblemEventID | Problem ID    | Event Reason         | Event Date    |
|---------------|---------------|----------------------|---------------|
|    1926144    | 3178766       | Reported             | 2019-08-12    | 
------------------------------------------------------------------------
|    2022750    | 3178766       | sell back            | 2019-08-13    |
------------------------------------------------------------------------
|    2022751    | 3178766       | Accepted as sell back| 2019-08-26    |
------------------------------------------------------------------------
|    2022899    | 3178766       | Finalized            | 2019-08-31    |
------------------------------------------------------------------------

我查询的结果如下：

|---------------|---------------|------------|-----------------------|------------|
|  Customer ID  | CustomerName  | Problem Id | Event Reason          | Event Date |
|---------------|---------------|------------|-----------------------|------------|
|    1234       | Johnathan     | 3178766    | Accepted as sell back | 2019-08-26 |
---------------------------------------------------------------------|------------|

提前感谢您的帮助。

Answer 1

如果您想要整个 table 的最新 "sell back" 活动，那么您可以加入、排序和限制：

select top (1)
    c.customer_id, 
    c.customer_name
    p.problem_id,
    pe.event_reason,
    pe.event_date
from customer c
inner join problem p on p.customer_id = c.customer_id
inner join problem_event pe on pe.problem_id = p.problem_id
where pe.event_reason like '%sell back%'
order by pe.event_date

还有其他方法可以理解您的问题。假设您想要每个客户 的最新 "sell back" 事件 ，那么这是一个 greatest-n-per-group 的问题。您可以使用 row_number():

select *
from (
    select
        c.customer_id, 
        c.customer_name
        p.problem_id,
        pe.event_reason,
        pe.event_date,
        row_number() over(partition by c.customer_id order by pe.event_date desc) rn
    from customer c
    inner join problem p on p.customer_id = c.customer_id
    inner join problem_event pe on pe.problem_id = p.problem_id
    where pe.event_reason like '%sell back%'
) t
where rn = 1
order by c.customer_id

每个问题 返回最新 "sell back" 事件的练习 ，这是对您的问题的最后可能解释，留给 reader！

加入3tables； select 来自第三 table 行，其中包含最新日期的特定字符串

Join 3 tables; select from third table row which contains specific string by latest date

sql

sql-server

join

select

sql-server-2008-r2