Question

Assume I have a log of something. Each record has a timestamp (MySQL data type TIMESTAMP) in the format date('Y-m-d H:i:s') (from PHP). I need to produce a report that looks like this:

===========================================
| Date                  | Total Sales     |
===========================================
| Thursday, Dec 1, 2011 | 100             |
-------------------------------------------
| Friday, Dec 2, 2011   | 200             |
-------------------------------------------
| Saturday, Dec 3, 2011 | 150             |
-------------------------------------------
... and so on ...

I assume I have to dynamically build the SQL from PHP, which is OK. I’m just not sure what the SQL would look like. Ideas?

Answer 1

How to count the number of records per day

This is what I originally thought you wanted. I’m leaving it here because it might be useful to other people.

You have a bunch of timestamps. You want to group them by individual days and get the number of records per day.

Assuming your timestamp field is named ts, you can do something like this:

SELECT COUNT(*), DAY(ts), MONTH(ts), YEAR(ts) FROM tableName
       GROUP BY YEAR(ts), MONTH(ts), DAY(ts);

How to generate daily reports for individual people

Ok this is what you really wanted. Let’s draw a sample table with some records:

ts                      person         sales
2011-12-01 10:00:00     John           10
2011-12-01 10:30:00     Mary           25
2011-12-01 11:00:00     John           20
2011-12-02 14:00:00     John           40

To get the daily totals for a particular person, you would do:

SELECT SUM(sales), DAY(ts), MONTH(ts), YEAR(ts) FROM tableName
       WHERE person='John'
       GROUP BY YEAR(ts), MONTH(ts), DAY(ts);

This is selecting records where person is John, grouped by unique days, and summing the sales value for those records. If you want reports for every person combined, just remove the WHERE clause.

Final note

You can simplify your SQL a little bit if you use the DATE type instead of the DATETIME type. I’m selecting and grouping by the day, month and year which I need to get using three separate functions. If you’re using the DATE type, calling these functions would be unnecessary and I could just select and group by ts directly. It’s up to you how you want to represent your data.