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Laurence MartinFlag for United Kingdom of Great Britain and Northern Ireland

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Can't nest InStr in a Left function

Why doesn't this expression work in an Access Query?

Postcode 1: Left(Trim([Clients].[Postcode]),InStr(1,[Clients].[Postcode]," ")-1)

I am getting an error that the expression is too complex.

If I put the InStr in a column of it's own and the Left with a constant for the length, they both work.

What I need to do is show the first part of the postcode.  In the UK we have postcodes (zipcodes) that have a space in the middle eg: NW1 4FS or B1 2GT or WC1Y 3CE.
Is there another way to parse the string?

Could it be data related?  There are some postcode fields that are empty or don't have a space
Avatar of John Tsioumpris
John Tsioumpris
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Postcode_1: Left(Trim([Clients].[Postcode]),InStr([Clients].[Postcode]," ")-1)

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Avatar of Jim Dettman (EE MVE)
Jim Dettman (EE MVE)
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It seems that the whole query is too complex and this just pushes it over the edge.  It has a massive From clause with lots of outer joins.

If I create a second query on the main one and add the calculated field then it works.

However, Jim's solution is better and so I'll build the IIf too.

Avatar of Bill Prew
Bill Prew

Try this, it should protect you from most problems with that field (blank, no embeded space, etc).

Postcode1:IIF(Trim([Clients].[Postcode])<>"",IIF(InStr(Trim([Clients].[Postcode])," ")>0,Left(Trim([Clients].[Postcode]),InStr(Trim([Clients].[Postcode])," ")-1),[Clients].[Postcode]),[Clients].[Postcode])

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This appends a space to the right of the [PostCode] to ensure that every record will have a value returned by the Instr( ) function.
I then take everything including to the left of that first space using the Left() function and then trim the spaces.
PostCode1:TRIM(Left([Clients].[PostCode] & " ", instr([Clients].[PostCode] & " ", " "))

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This ensures that Trim will work, because there is no chance that a NULL will be processed.
That's a great approach.  Get's rid of the IIF() to.

Thanks, Jim.  I use this approach alot when using instr() or instrrev().  It generally takes some thought to get it right, but once I do, it generally works like a charm.

I guess the only note on that clever approach is that NULL values become "empty strings" in the process.  That might be a good thing, or a bad thing, depending on the use case.