使用 MySQL 从一列到多列的数据计数？

Question

我无法理解如何将不同的活动拆分并计入单独的列中。这是开头table:

+------------+---------+
| CustomerID |Activity |
+------------+---------+
|          1 | Click   |
|          1 | View    |
|          1 | Inquiry |
|          2 | Click   |
|          2 | View    |
|          3 | Click   |
|          3 | Click   |
+------------+---------+

我希望能够将其转换为：

+------------+------+-------+---------+
| CustomerID | View | Click | Inquiry |
+------------+------+-------+---------+
|          1 |    1 |     1 |       1 |
|          2 |    1 |     1 |       0 |
|          3 |    0 |     2 |       0 |
+------------+------+-------+---------+

Answer 1

您可以使用 case statement 和 sum，例如，

select 
    `CustomerID`,
    sum(case when `Activity` = 'View' then 1 else 0 end) `View`,
    sum(case when `Activity` = 'Click' then 1 else 0 end) `Click`,
    sum(case when `Activity` = 'Inquiry' then 1 else 0 end) `Inquiry`
from `tbl`
group by `CustomerID`
order by `CustomerID`

输出为

CustomerID  View    Click   Inquiry
1             1     1       1
2             1     1       0
3             0     2       0

使用 MySQL 从一列到多列的数据计数？

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