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  1. #1
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    We have an SQL database with an ODBC link to Access 2007. I am preparing some documentation, and SQL Server 2005 Management Studio lists an "Allow Nulls" parameter for all fields whereas Access 2007 lists an "Allow Zero Length" parameter for text fields only, and some fields are listed as "Allow Nulls = No" in SQL Server but "Allow Zero Length = Yes" in Access. How are these two parameters related, why does SQL Server list only the one and Access only the other, and which would an application developer normally need to know?

    Also, Access lists a "Required" parameter, except for bit fields, but SQL Server does not seem to list this; does it refer to a requirement of Access or of the database?

  2. #2
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    I believe that the Access Required and the SQL "Allow Nulls" are equivalent (but the converse of each other). If something is Not Required, you can leave it empty, which means its value remains at Null.
    So this is the more important of the two. A field should only be Required if you are sure that you will always have a value to put in there.

    A zero length string is : "" A pair of double quotes with nothing between them. If you allow them in Access something that looks like it is Null may not be. Imported data can often contain such values so allowing them can make importing easier.
    Regards
    John



  3. #3
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    Thanks for your reply.

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