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SQL-clause

majala
majala asked
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Last Modified: 2010-04-30
Here is a criteria how I open my recordset:
criteria = "SELECT [Date], [Time], " + MyField + " FROM " + MyDB + " WHERE Time >='" + StartTime + "' AND Time <='" + EndTime + "' AND Date =#" + MyDate + "#"

I would like to add there one variable called Step.
I mean that if there is field in my database for every 1 minutes and I wanna open recordset only for every 15 minutes (Step is 15 minutes).
Is this even possible?? If it is, would you give me an example!

Thanks in advance!
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Commented:
to clear this up a bit, you want to do what? only get the record if the step variable = 15, or every multiple of 15, or is this step information in the Time field?

Author

Commented:
Here's example:
Recordset takes these datas now (if Starttime is 12:00, EndTime is 17:00 and Date is 24/6).
Date         Time       MyField
24.6         12:00      .....
24.6         12:01      .....
24.6         12:02      .....



24.6         17:00      .....
But I wanna take only these datas (if Step is 15):
Date         Time       MyField
24.6         12:00      .....
24.6         12:15      .....
24.6         12:30      .....
24.6         12:45      .....



24.6         17:00      .....

If this isn't possible, any other suggestions?

Commented:
insert this into your where clause

AND (((datepart("n",Time)) mod 15) = 0)

bon chance

Author

Commented:
That worked almost fine but there were a few things:

How I put it if I want that Step variable there:
AND (((datepart("n",Time)) mod " + Step + ") = 0), this didn't work?

This didn't work also:
(((datepart("n",Time)) mod 120) = 0)
Could it be something like:
(((datepart("h",Time)) mod 2) = 0)

Here is also one example how I want that recordset to open:
Date         Time       MyField
25.6         12:00      .....
26.6         12:00      .....
27.6         12:00      .....
28.6         12:00      .....

In my program there is a combobox where user can choose that Step-variable (10 minutes, 30 minutes, 1 hour, 1 day, 1 week)
Commented:
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Author

Commented:
If you could still tell me how I can do this:
AND (((datepart("n",Time)) mod " + Step + ") = 0)

I don't understand why this don't work. That Step variable is Variant.

Commented:
ok 2 errors
1. syntax for "n" should be 'n'(my fault i generated this in access)
2. If datediff or datepart = 0 then then the mod will always be  crop up, since the bigger the number the more chance something = to 0, so datepart will return all times with XX:00 and datediff will return all times were for eg (12:00 = 12:00)
3. If datediff is big enough, then mulitple false values will will be a factor, and hence mod = 0

the best i can do is

Sqlstr = "SELECT * From Table1 Where (Table1.Date = Date) And (Table1.Time >= #12:00:00 PM#) And (Table1.Time <= #5:00:00 PM#)AND (((Datediff('n',#" & mydate & " " & starttime & "#,Table1.time) ) mod " & step & ")  = 0)"

where step = number of minutes in step eg. 1440 for one day

You may need to combine the table1 time and date to avoid erorrs as stated in 3. and 2.  

Author

Commented:
Yes I noticed at the beginning that syntax "n" didn't work. I got it work when I did it like ""n"" but that 'n' seems to work also.
Now that "... mod "& step &"..." works also.

I didn't quite understand your second and third errors.

Thanks!

Commented:
well, mod is a function that finds the remainder of 2 numbers, if the 1st number is 0 then there can be no remainder, so the expression evaluates to 0 and thus passes any record that matches.
so if you ask for the minutes datepart of 12:00 = 0 and, 0 mod 120 = 0, so the database thinks this record is ok and thus passes it back to your VB recordset

This also happens with datediff function if you give two times, if they are the same eg 12:00 and 12:00 then even though they have different dates and thus are different by n* 1440 minutes, the function knows nothing about their dates and just thinks they are on the same day, so you get 0 and the same problem as above.
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