I've got 2 MySQL tables: Employees, and Mileage. Mileage records trips
for
employees and there may be 0 or more Mileage rows for each Employee
row. The Mileage table has a trip_date column. For testing purposes,
the
trip_date column in all rows is set to 2002-03-01.
There are currently 15 rows in the Employees table.
I want the result of the following select to be 15 rows (1 for each
employee, whether or not there are any rows in the Mileage table for
that
employee). If I take the "where" clause out, I get all 15 rows
(including
a number of rows where sum(m.miles) = 0 (which is what I want). If I
leave
the "where" clause in, however, I don't get employees with sum(m.miles)
= 0
(even though the "where" clause should include all of the Mileage rows).
(Only 3 Employees actually have corresponding rows in the Mileage table,
and I only get 3 rows back.)
select e.id,lname,sum(m.miles) from employees e
left join mileage m on e.id=m.id
where month(m.trip_date) = 3
and substring(year(m.trip_date),3,2) = '02'
group by e.id;
I need to select by month/year from the Mileage table. Any idea how the
"select" can be modified to include rows for all of the Employees?
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