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MySQL / ASP - Invalid use of Null

Posted on 2009-07-08
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Last Modified: 2012-06-21
I am getting an "invalid use of null" error with the following code.

cottage_array = split((enquiries.Fields.Item("enquirycottage").Value),",")

There is definitely a value in the column.

If I do this instead I don't get the error:

dim str_enq : str_enq = (enquiries.Fields.Item("enquirycottage").Value)
cottage_array = split(str_enq,",")

I am using MySQL 5.1.

Any ideas..?
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Question by:Orroland
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LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 24808930
you have to first check if the field value is null or not.

this might work as shortcut:
cottage_array = split(("" & enquiries.Fields.Item("enquirycottage").Value),",")

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LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 24808933
otherwise:
dim v
v = ""
if not isnull(enquiries.Fields.Item("enquirycottage").Value) then
  v = enquiries.Fields.Item("enquirycottage").Value
end if
cottage_array = split(v,",")

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Author Comment

by:Orroland
ID: 24808971
Thanks for the amazingly fast response.

Yes, I see that this workaround will fix the problem.  However, I don't understand why it is happening.  The field is a MySQL text field and DEFINITELY has a value.

If have just found that even if I do a response.write of the field value before the split() it works.  It seems that I need to extract the field value before it will work.
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LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 24808986
text field, you say? which size?
via odbc driver? which version?

that could be the problem... with the newest mysql odbc driver, or better the oledb provider, it should work better.
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Author Comment

by:Orroland
ID: 24809095
My connection string:

driver={MySQL ODBC 5.1 Driver};server=xxx;uid=xxx; pwd=xxx;database=xxx;option=3;

How do I use the OLEDB provider?
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LVL 143

Accepted Solution

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Guy Hengel [angelIII / a3] earned 2000 total points
ID: 24809117
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Author Comment

by:Orroland
ID: 24809251
OK, I have downloaded, installed and activated their Provider.

I now just get a (very unhelpful) error when I try to open a recordset:

800410ff

My new connection string is:

Provider=MySQL Provider; Data Source=xxx; User ID =xxx; Password=xxx; Initial Catalog=xxx;

Does this look OK?
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LVL 9

Expert Comment

by:rg20
ID: 24809619
I seem to recall an error with Oracle readers that once you read the value, you cant read it again, hence a null.

you might store it to a local variable then split it.  hence you dont' get the error
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