Count Monthly Visitor based on their Purpose - mysql

Question

Hi everybody,
I have this visitors table:
ID | Date | Purpose
1 | 20/10/2016 | Purpose1
2 | 22/10/2016 | Purpose1
3 | 25/10/2016 | Purpose2
4 | 12/11/2016 | Purpose1
5 | 14/11/2016 | Purpose2
6 | 16/11/2016 | Purpose2
Currently I'm using this query:
select case
when date like '%/10/2016' then '10/2016'
when date like '%/11/2016' then '11/2016'
end as month, count(*) as total
from visitors
where
date like '%/10/2016'
or date like '%/11/2016'
GROUP by month
I can only get month and total column count from query above. How can I achieve this output?
Month | Total | Purpose1 | Purpose2
10/2016 | 3 | 2 | 1
11/2016 | 3 | 1 | 2
Thanks!

Answer 1

Consider the following...
DROP TABLE IF EXISTS my_table;
CREATE TABLE my_table
(ID INT NOT NULL AUTO_INCREMENT PRIMARY KEY
,Date DATE NOT NULL
,Purpose VARCHAR(12) NOT NULL
);
INSERT INTO my_table VALUES
(1,'2016-10-20','Purpose1'),
(2,'2016-10-22','Purpose1'),
(3,'2016-10-25','Purpose2'),
(4,'2016-11-12','Purpose1'),
(5,'2016-11-14','Purpose2'),
(6,'2016-11-16','Purpose2');
SELECT DATE_FORMAT(date,'%Y-%m') month
, SUM(purpose = 'purpose1') purpose1
, SUM(purpose = 'purpose2') purpose2
, COUNT(*) total
FROM my_table
GROUP
BY month;
+---------+----------+----------+-------+
| month | purpose1 | purpose2 | total |
+---------+----------+----------+-------+
| 2016-10 | 2 | 1 | 3 |
| 2016-11 | 1 | 2 | 3 |
+---------+----------+----------+-------+
..or (and in my view, better, provided you have access to application code)...
SELECT DATE_FORMAT(date,'%Y-%m') month
, purpose
, COUNT(*) total
FROM my_table
GROUP
BY month
, purpose;
+---------+----------+-------+
| month | purpose | total |
+---------+----------+-------+
| 2016-10 | Purpose1 | 2 |
| 2016-10 | Purpose2 | 1 |
| 2016-11 | Purpose1 | 1 |
| 2016-11 | Purpose2 | 2 |
+---------+----------+-------+

Answer 2

Transposing tables isn't very fast. It is better to do so in some small program.
If you do a
select case
when date like '%/10/2016' then '10/2016'
when date like '%/11/2016' then '11/2016'
end as month, count(*) as total, Purpose
from visitors
where
date like '%/10/2016'
or date like '%/11/2016'
GROUP by month, Purpose
You'll have a good starting point.
You might need to add an ORDER BY clause (depending on your DBMS).
If (and only if) you only have two purposes in your table and the table isn't huge in size, you can create two views and join them.