How to use group concat with group by? - mysql

Question

Here my table is having filed as following:
employee_id,
expense_id,
expense_type,
expense_cost,
expense_date and etc,
And i want to display as month wise expenses as row wise for particular employee.
in my table data has stored like
2wheeler 01/03/2014 99 Santhosh 4493.00 March 500.00
Auto 03/02/2014 99 Santhosh 0.00 February 80.00
Food 01/02/2014 99 Santhosh 0.00 February 200.00
Phone Expense 01/03/2014 99 Santhosh 0.00 March 500.00
In this table i want to get out as
single user row with concat of expense type and sum of cost for every month that mean : march have single row with concat of expense type & sum of cost.

Answer 1

I would suggest doing a sub query that sums up all the occurances of an expenses per employee per month per expense. Then use that as a source to get the list of employees, months and the GROUP_CONCATed list of expense types and the total cost of them.
Like this:-
SELECT employee_id, expense_month, GROUP_CONCAT(CONCAT_WS('=', expense_type, monthly_exployee_expense))
FROM
(
SELECT employee_id, MONTH(expense_date) AS expense_month, expense_type, SUM(expense_cost) AS monthly_exployee_expense
FROM some_table
GROUP BY employee_id, expense_month, expense_type
) Sub1
GROUP BY employee_id, expense_month
EDIT
Reading you comment it seems that you need an expense listed even when an employee has not incurred that expense that month.
To do that I think you will need to cross join the employees (I have assumed a table name of tbl_employee) with the table of expenses types, and also all the possible months (assuming you want a row for a month for an employee when that employee has had no expenses that month). I have got the possible months by just selecting the distinct year / month from the table listing all the expenses (but there are other ways to get this - depends if there are any months where no employees had any expenses and if you want to put these out anyway).
Once those are cross joined to get every combination of employee, month and expense you can left join the actual expenses in the sub query, and then do the GROUP_CONCAT much as before.
Not tested, but something like this:-
SELECT employee_id, expense_month, GROUP_CONCAT(CONCAT_WS('=', exp_type_text, monthly_exployee_expense))
FROM
(
SELECT tbl_employee.employee_id, expense_months.expense_month, tbl_expense_type.exp_type_id, tbl_expense_type.exp_type_text, SUM(expense_cost) AS monthly_exployee_expense
FROM tbl_employee
CROSS JOIN tbl_expense_type
CROSS JOIN
(
SELECT DISTINCT DATE_FORMAT(expense_date, '%Y%m') AS expense_month
FROM some_table
) expense_months
LEFT OUTER JOIN some_table
ON tbl_employee.employee_id = some_table.employee_id
AND tbl_expense_type.exp_type_id = some_table.expense_type
AND expense_months.expense_month = DATE_FORMAT(some_table.expense_date, '%Y%m')
GROUP BY tbl_employee.employee_id, expense_months.expense_month, tbl_expense_type.exp_type_id, tbl_expense_type.exp_type_text
) Sub1
GROUP BY employee_id, expense_month