SQL 透视/反透视？

Posted 2023-04-12

【中文标题】SQL 透视/反透视？

【英文标题】：SQL pivot/Unpivot?

【发布时间】：2020-09-29 09:35:49

【问题描述】：

真的希望有人可以帮助我，我的表格结构如下：

检索此数据的查询是：

SELECT

[Pattern Number]
,Sunday
,Monday
,Tuesday
,Wednesday
,Thursday
,Friday
,Saturday

FROM Access.Pattern_Details
WHERE [Pattern Number] = 4

+----------------+--------+--------+---------+-----------+----------+--------+----------+
| Pattern Number | Sunday | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday |
+----------------+--------+--------+---------+-----------+----------+--------+----------+
|              4 |      0 |      1 |       1 |         1 |        1 |      1 |        0 |
+----------------+--------+--------+---------+-----------+----------+--------+----------+

我想变成这样：

+----------------+------------+-----------+
| Pattern Number | WorkingDay |    Day    |
+----------------+------------+-----------+
|              4 |          0 | Sunday    |
|              4 |          1 | Monday    |
|              4 |          1 | Tuesday   |
|              4 |          1 | Wednesday |
|              4 |          1 | Thursday  |
|              4 |          1 | Friday    |
|              4 |          0 | Saturday  |
+----------------+------------+-----------+

我已经尝试过PIVOT/UNPIVOT，这感觉是正确的方向，但我真的很想知道如何获得结果:(

【问题讨论】：

您好 Cordy，请在您的问题中包含您尝试过的查询。

请用您正在运行的数据库标记您的问题：mysql、oracle、postgresql...？答案取决于供应商。

UNION ALL 是一种简单的方法。

如果您尝试过某事并遇到问题，请展示该内容并描述该问题。 “真正为如何获得结果而苦苦挣扎”并不是读者可以做任何事情的描述

【参考方案1】：

在 SQL Server 中，我会推荐cross apply 和values()：

select pd.[Pattern Number], x.*
from Access.Pattern_Details pd
cross apply (values 
    ('Sunday',    Sunday), 
    ('Monday',    Monday),
    ('Tuesday',   Tuesday),
    ('Wednesday', Wednesday),
    ('Thursday',  Thursday),
    ('Friday',    Friday),
    ('Saturday',  Saturday)
) x(day, workingDay)
where pd.[Pattern Number] = 4

【参考方案2】：

你可以使用UNPIVOT:

SELECT [Pattern Number], [Working Day], [Day] 
FROM
(
  SELECT 4 [Pattern Number], 0 Sunday, 1 Monday, 1 Tuesday, 1 Wednesday, 1 Thursday, 1 Friday, 0 Saturday
) pvt
UNPIVOT([Working Day] FOR [Day] IN ([Sunday], [Monday], [Tuesday], [Wednesday], [Thursday], [Friday], [Saturday])) unpvt

db<>fiddle

UNPIVOT 有很好的文档和解释。见：Using Pivot and Unpivot - SQL Server