Update query to determine if date is a weekend

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
ktjamms2Asked:
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Phillip BurtonDirector, Practice Manager and Computing ConsultantCommented:
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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ktjamms2Author Commented:
Actually I need:

SET [Copy Of IMPORT_Current].WATER = [Copy Of IMPORT_Current].WATER of the day before
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Phillip BurtonDirector, Practice Manager and Computing ConsultantCommented:
Which is why there is a -1 in line 2.
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ktjamms2Author 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
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Phillip BurtonDirector, Practice Manager and Computing ConsultantCommented:
What do you mean, "number value"?
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ktjamms2Author Commented:
rephrased:
Set Saturday's water values to Friday's water values
and Set Sunday's water values to Monday's water values
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ktjamms2Author 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
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Phillip BurtonDirector, Practice Manager and Computing ConsultantCommented:
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,
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hnasrCommented:
List 3 records, and show required output.
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ktjamms2Author 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.
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Phillip BurtonDirector, Practice Manager and Computing ConsultantCommented:
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,
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ktjamms2Author 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?
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Phillip BurtonDirector, Practice Manager and Computing ConsultantCommented:
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]

Open in new window


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]

Open in new window

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