How to make relation to a column(s) depending on value - sql

Question

4I have these tables :
day_shift
id_dshift dshift_name on_duty off_duty in_start in_end out_start out_end workday
1001 ds_normal 7:00 15:00 7:00 10:00 11:00 20:00 1
1002 ds_Saturday 7:00 14:00 7:00 10:00 11:00 14:00 1
week_shift
id_wshift wshift_name mon tue wed thu fri sat sun
2001 ws_normal 1001 1001 1001 1001 1001 1002 1001
2002 ws_2013_w1 0 1001 1001 1001 1001 1001 0
2003 ws_2013_w2 1003 1001 1001 1001 1001 1002 1001
daily_attendance
emp_id checkdate in out emp_shift_id
10 15/06/2013 7:10 15:05 2001 <-- saturday
10 16/06/2013 7:05 15:03 2001 <-- sunday
what I want is having a result like this :
emp_id checkdate in out on_duty off_duty
10 15/06/2013 7:10 15:05 07:00 14:00
10 16/06/2013 7:30 14:30 07:00 15:00
in first row of daily_attendance, since the weekday is saturday so i want to get the value of week_shift.sat (1002)
if the weekday is sunday, i want to get the value of week_shift.sun (1001)
so I get the on_duty and off_duty values from day_shift
How to do it in query?

Answer 1

The trick here would be to create a saved query in Access named [week_shift_transformed] to transform your [week_shift] table into separate rows for each day of the week:
SELECT id_wshift, wshift_name, 1 AS [weekday], [sun] as id_dshift FROM week_shift
UNION ALL
SELECT id_wshift, wshift_name, 2 AS [weekday], [mon] as id_dshift FROM week_shift
UNION ALL
SELECT id_wshift, wshift_name, 3 AS [weekday], [tue] as id_dshift FROM week_shift
UNION ALL
SELECT id_wshift, wshift_name, 4 AS [weekday], [wed] as id_dshift FROM week_shift
UNION ALL
SELECT id_wshift, wshift_name, 5 AS [weekday], [thu] as id_dshift FROM week_shift
UNION ALL
SELECT id_wshift, wshift_name, 6 AS [weekday], [fri] as id_dshift FROM week_shift
UNION ALL
SELECT id_wshift, wshift_name, 7 AS [weekday], [sat] as id_dshift FROM week_shift
That will give you
id_wshift wshift_name weekday id_dshift
--------- ----------- ------- ---------
2001 ws_normal 1 1001
2002 ws_2013_w1 1 0
2003 ws_2013_w2 1 1001
2001 ws_normal 2 1001
2002 ws_2013_w1 2 0
2003 ws_2013_w2 2 1003
2001 ws_normal 3 1001
2002 ws_2013_w1 3 1001
2003 ws_2013_w2 3 1001
2001 ws_normal 4 1001
2002 ws_2013_w1 4 1001
2003 ws_2013_w2 4 1001
2001 ws_normal 5 1001
2002 ws_2013_w1 5 1001
2003 ws_2013_w2 5 1001
2001 ws_normal 6 1001
2002 ws_2013_w1 6 1001
2003 ws_2013_w2 6 1001
2001 ws_normal 7 1002
2002 ws_2013_w1 7 1001
2003 ws_2013_w2 7 1002
Then you can use a query like this:
SELECT da.emp_id, da.checkdate, da.in, da.out, ds.on_duty, ds.off_duty
FROM
daily_attendance da
INNER JOIN
(
week_shift_transformed wtt
INNER JOIN
day_shift ds
ON ds.id_dshift = wtt.id_dshift
)
ON wtt.weekday = Weekday(da.checkdate)
AND wtt.id_wshift = da.emp_shift_id