Updating an Access database based on a sub-select

[Kyle Wood]

I have an Access database which contains every date between 01/01/2009 and 21/12/2029. In a 2nd column is a char value indicating whether the date is a working day or not. I need to decide whether xmas & boxing day fall on a non-working day and if so adjust the working day column value. I have the following to calculate the adjusted dates:

SELECT switch((DATEPART("w",FullDate,2) In (6,7)),DATEADD("d",+2,FullDate),(DATEPART("w",FullDate,2) Not In (6,7)),FullDate)
FROM UKWorkingDays
WHERE DATEPART("m",FullDate,2)=12 And DATEPART("d",FullDate,2) In (25,26);

If I wrap this in an update statement the SQL appears to execute but does nothing at all

UPDATE UKWorkingDays SET WorkingDay = "B"
WHERE FullDate in
(

SELECT switch((DATEPART("w",FullDate,2) In (6,7)),DATEADD("d",+2,FullDate),(DATEPART("w",FullDate,2) Not In (6,7)),FullDate)
FROM UKWorkingDays
WHERE DATEPART("m",FullDate,2)=12 And DATEPART("d",FullDate,2) In (25,26)

);

Can anyone give me any assistance please ?

[Mycroft Holmes]

Ew Access again - and a newer version than I have worked with. Some thoughts. Why do you have the switch (what is switch doing in SQL code) in the select portion, surely you want that in the where clause.

Select Fulldate
From UKWorkingDays
Where fulldate in (filter 25/6) and weekday in (filter weekdays)

I leave it to to grasshopper to fix the filter.

[Kyle Wood]

Thanks for the reply Mycroft but I'm not sure that it is of much help. Take this year for example. 25/12 is a Friday, 26/12 is a Saturday so 28/12 is actually a holiday not a working day. My inner select statement returns 2 rows correctly containing Friday 25/12 and Monday 28/12. I then have to check every row in the table against these returned values and if equal mark the date as a non-working day (my outer update). The inner select works a treat so I thought an update statement where date in (inner select) would achieve what I wanted but for some reason it appears to do nothing, no rows returned updated and no exception thrown. Maybe its looping too many times and would eventually finish. I'll have to re-visit my code and see if there's a better way.

[Kyle Wood]

More on this.. I've just stripped out all but this years dates and run my query which has done exactly as I expected and updated 25 & 28/12. I guess its just baulking at the number of repetitions it has to perform on the full table so I'm on the right track but do need to improve the code.