How do I perform this join query? - mysql

Question

I have a table leave_form which looks like:
type id reporting_id leave_bal from_date_id leave_from to_date_id leave_to number leave_for status applied_dates_id pendays
personal 99 6 10 1023 full day 1313 full day 10 personal yes 1026 null
I have separate table for dates, so that I can refer these dates into leave_form. My leave_date table looks like:
date_id(AI) dates(UK)
1025 2016-02-18
1301 2016-02-20
1218 2016-02-16
This date_id I have inserted into from_date_id, to_date_id, applied_dates_id columns in leave_form table i.e. all dates are inserted into leave_date table and from this table I am only referring the date_id into leave_form table.
There is also a table that keeps the emp_code and emp_name. My personal table is:
id(AI) emp_code(PK) emp_name
99 K0209 Nijo
When I am trying to fetch the date for from_date_id, to_date_id, applied_dates_id column from leave_form table I don't get any values.
My query for fetching the dates is:
select g.type, a.emp_code, h.rm_id, h.rm_name, g.leave_bal, i1.dates as from_date,
g.leave_from, i2.dates as to_date, g.leave_to, g.number, g.leave_for, g.status,
i3.dates as applied_date, g.pendays
from personal a
inner join leave_form g
on a.id = g.id
inner join inform_to_rm h
on h.reporting_id = g.reporting_id
inner join leave_dates i1
on i1.dates = g.from_date_id
inner join leave_dates i2
on i2.dates = g.to_date_id
inner join leave_dates i3
on i3.dates = g.applied_dates_id
where a.emp_code = 'K0209';
It shows me result like:
type, emp_code, rm_id, rm_name, leave_bal, from_date, leave_from, to_date, leave_to, number, leave_for, status, applied_date, pendays
i.e no data gets returned when I am executing this query.

Answer 1

I would agree with one of the comments to the question. I would recommend referencing the date directly in the leave_form table instead of a FK to a table with dates. But back to the question. You haven't described all of your tables completely, so it is possible that there are multiple problems that I can't see, however, there is definitely one problem.
Your query joins on
inner join leave_dates i1
on i1.dates = g.from_date_id
inner join leave_dates i2
on i2.dates = g.to_date_id
inner join leave_dates i3
on i3.dates = g.applied_dates_id
This is incorrect. leave_dates.dates is the actual DATE, while the columns that you are joining on (leave_form.from_date_id, leave_form.to_date_id, leave_form.applied_dates_id) are foreign key references.
For example, 1023 does not equal 2016-02-18 so you get no match. Replacing the above query-snippet with the following would correct this particular problem.
inner join leave_dates i1
on i1.date_id = g.from_date_id
inner join leave_dates i2
on i2.date_id = g.to_date_id
inner join leave_dates i3
on i3.date_id = g.applied_dates_id