如何使用 SQL 将这四行转换为列

Question

我想获取步骤 table 的行作为新 table

的列

步数table

ID |Steps | Steps_Date
1 | Create | 5/9/2020
1 |Schedule | 5/11/2020
1| Complete | 5/12/2020
1| Request | 5/10/2020
2| Request | 5/12/2021

这些是 table 转换为列的步骤的行。

新建table

ID | Create | Request | Schedule | Complete
1 | 5/9/2020|5/10/2020|5/11/2020|5/12/2020
2 | Null | 5/12/2021 | Null | Null

Answer 1

做一个GROUP BY。使用case表达式做条件聚合:

select id,
       max(case when Steps = 'Create'   then Steps_Date end) as create_date,
       max(case when Steps = 'Request'  then Steps_Date end) as Request_date,
       max(case when Steps = 'Schedule' then Steps_Date end) as Schedule_date,
       max(case when Steps = 'Complete' then Steps_Date end) as Complete_date
from Steps_table
group by id

如何使用 SQL 将这四行转换为列

How can I convert these four rows into columns using SQL

sql

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