Update query to determine if date is a weekend

ktjamms2
ktjamms2 used Ask the Experts™
on
I want to update a field's value to the previous day's field value (if on a Saturday) or to the value of the day after (if on a Sunday). I'm not sure of the correct syntax.

I tried this:
UPDATE [Copy Of IMPORT_Current] SET [Copy Of IMPORT_Current].WATER = DateAdd("d",-1, [Copy Of IMPORT_Current]![DATE])
IIf (Weekday([Copy Of IMPORT_Current]![DATE],1) =7
 
but it's not the correct syntax and it doesn't utilize the "OR" criteria I'm aiming for.

Any help would be great!
Thanks,
KT
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Phillip BurtonDirector, Practice Manager and Computing Consultant
Awarded 2014
Top Expert 2014

Commented:
Try this:

UPDATE [Copy Of IMPORT_Current] SET [Copy Of IMPORT_Current].WATER = DateAdd("d",
iif(Weekday([Copy Of IMPORT_Current]![DATE],1) =7,-1,iif(Weekday([Copy Of IMPORT_Current]![DATE],1) =1,1,0)), 
[Copy Of IMPORT_Current]![DATE])

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Author

Commented:
Actually I need:

SET [Copy Of IMPORT_Current].WATER = [Copy Of IMPORT_Current].WATER of the day before
Phillip BurtonDirector, Practice Manager and Computing Consultant
Awarded 2014
Top Expert 2014

Commented:
Which is why there is a -1 in line 2.
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Author

Commented:
I'm not sure what you have, but it looks like its setting the value to a date.  I need the value set to the number value of the corresponding date:

SET [Copy Of IMPORT_Current].WATER = [Copy Of IMPORT_Current].WATER of the day before if the [Copy Of IMPORT_Current]![DATE] is a Saturday

or

SET [Copy Of IMPORT_Current].WATER = [Copy Of IMPORT_Current].WATER of the day after if the [Copy Of IMPORT_Current]![DATE] is a Sunday
Phillip BurtonDirector, Practice Manager and Computing Consultant
Awarded 2014
Top Expert 2014

Commented:
What do you mean, "number value"?

Author

Commented:
rephrased:
Set Saturday's water values to Friday's water values
and Set Sunday's water values to Monday's water values

Author

Commented:
Explanation:
I don't get numbers for weekends. So, I want to just use the numbers for the day before or from the day after depending  on whether it's Saturday or Sunday
Phillip BurtonDirector, Practice Manager and Computing Consultant
Awarded 2014
Top Expert 2014

Commented:
Now that you have the relevant date, in a second query, you do a Left Join with the original table to get the relevant date's value,
Hamed NasrRetired IT Professional

Commented:
List 3 records, and show required output.

Author

Commented:
ID            DATE                  WATER

20            11/1/2014            0
20            11/2/2014            225
20            11/3/2014            100      
20            11/4/2014            200
20            11/5/2014            350
20            11/6/2014            500
20            11/7/2014            220
20            11/8/2014            0

11/1/2014 IS A SUNDAY. THE WATER NEEDS TO BE UPDATED TO THE NEXT DAY'S WATER VALUE (11/2/2014, MONDAY). THAT VALUE WOULD BE 225

11/8/2014 IS A SATURDAY. THE WATER NEEDS TO BE UPDATED TO THE PREVIOUS DAY'S WATER VALUE (11/7/2014, FRIDAY). THAT VALUE WOULD BE 220

THERE ARE MULTIPLE IDs AND DATES IN THE TABLE. I ONLY SHOWED AN EXAMPLE OF ONE CASE FOR A WEEK IN THIS EXAMPLE.
Phillip BurtonDirector, Practice Manager and Computing Consultant
Awarded 2014
Top Expert 2014

Commented:
Now that you have the relevant date, in a second query, you do a Left Join with the original table to get the relevant date's value,

Author

Commented:
I don't understand what you are saying----- "Now that you have the relevant date, in a second query, you do a Left Join with the original table to get the relevant date's value, "

Could you show the SQL code?
Director, Practice Manager and Computing Consultant
Awarded 2014
Top Expert 2014
Commented:
Your original table is [Copy Of IMPORT_Current]

You create a new query, Query1, with the following code:
Select *, DateAdd("d",iif(Weekday([DATE],1) =7,-1,iif(Weekday([DATE],1) =1,1,0)), [DATE]) as NewDate
From [Copy Of IMPORT_Current]

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Then you have another query which does the join:
Select Query1.*, [Copy Of IMPORT_Current].WATER
From Query1
Left join [Copy Of IMPORT_Current]
ON Query1.NewDate = [Copy Of IMPORT_Current].[DATE]

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