PHP选择并按日期（月份和年份）以及用户分组

Question

I have a table that has info like this:

id | staff_id | start_date
1  | 14       | 2015-04-02 00:00:00
2  | 16       | 2015-04-15 00:00:00
3  | 14       | 2015-05-31 00:00:00
4  | 12       | 2015-05-04 00:00:00

What I am trying to do is select and count all entries made by each staff member and group them by month and year so it would display like this:

Staff Member  | 12  | 14  | 16
2015-04       | 0   | 1   | 1
2015-05       | 1   | 1   | 0

Can anyone please help me to figure out how to generate this? I just cant figure out how to create a new column for each staff member and also a row for each month/year.

Answer 1

This is a pivot query, but a bit complicated because of the dates:

select date_format(start_date, '%Y-%m') as yyyymm,
       sum(staff_id = 12) as `12`, sum(staff_id = 14) as `14`,
       sum(staff_id = 16) as `16`
from table t
group by yyyymm;

If you don't know the staff ids in advance, then you'll need to use dynamic SQL. Google "MySQL dynamic pivot" to see how to do that.

Answer 2

This is called cross tabulated query (aka pivot table). MySql does not natively support such transformations.

Possible solutions: 1. Generate the counts by user and month in the traditional way and then use php to transform the data into its final resultset. 2. Use a spreadsheet program (eg. Excel) to do the transformation for you again based on the traditional dataset. 3. There are ways to do it in MySql, see link1 , link2

The second link is a SO link.