MS Access SQL-比较一般日期和短日期

Question

I need to compare the 2 different date types ( General Date & Short Date ).

I tried to use FORMAT() to able to get the converted date, but you can't use it in WHERE Clause.

"SELECT DT, Item, N, InvoiceNum, FORMAT(DT, 'Short Date') as DT_SD FROM itemHistory WHERE DT_SD='#" & selectedDate & "#')"

Answer 1

You can't use Alias in your where because your alias use in your select. Unless you wrap in to subquery

Reason :

Where : conditions are evaluated and rows that do not match are removed

So your where statement see as your row not your aliasing. Use the full expression instead as stated by @Rene.

"SELECT DT, Item, N, InvoiceNum FROM itemHistory 
WHERE FORMAT(DT, 'Short Date') = #" & selectedDate & "#)"

Answer 2

You should always handle dates as dates, not text.

For Access SQL, you will have to use a properly formatted string expression for the date values:

"SELECT DT, Item, N, InvoiceNum FROM itemHistory WHERE DateDiff('d', DT, #" & Format(selectedDate, "yyyy\/mm\/dd") & "#) = 0"

If DT never contains a time value , this can be reduced to:

"SELECT DT, Item, N, InvoiceNum FROM itemHistory WHERE DT = #" & Format(selectedDate, "yyyy\/mm\/dd") & "#"

This will run faster, if you have an index on field DT.