使用MySQL從一列到多列的數據計數？

Question

我無法理解如何將不同的活動拆分和計算到不同的列中。 這是開始表：

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

我希望能夠將其轉換為：

+------------+------+-------+---------+
| 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 ，

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`

輸出是

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