Microsoft KB Archive/121332

= ACC: AutoLookup Query Not Performed with 1-to-1 Relationship =

Article ID: 121332

Article Last Modified on 1/19/2007

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APPLIES TO


 * Microsoft Access 2.0 Standard Edition
 * Microsoft Access 95 Standard Edition
 * Microsoft Access 97 Standard Edition

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This article was previously published under Q121332



Moderate: Requires basic macro, coding, and interoperability skills.



SYMPTOMS
Microsoft Access will not perform an AutoLookup query if it determines that the tables in the query have a one-to-one relationship.



CAUSE
Microsoft Access determines the relationship between the tables in the query by examining the indexes on the join fields. Microsoft Access will ignore the relationship that you specify when it is determining whether to perform an AutoLookup query. If your tables have one of the following index combinations, Microsoft Access will not perform an AutoLookup query:

  Table 1                  Table 2 --  --   Primary Key              Primary Key Primary Key             Indexed, No Duplicates Indexed, No Duplicates  Primary Key



RESOLUTION
To cause Microsoft Access to perform an AutoLookup query, make sure that the foreign key is neither indexed as the Primary Key nor Indexed, No Duplicates. It may be necessary to add a unique index to the foreign key on the "many" side of a relationship in order to maintain the integrity of the data. In this case, AutoLookup will not work and a workaround will have to be used.



MORE INFORMATION
Consider the following tables:

  Employees     Offices --  --   EmployeeID    OfficeID LastName     AssignedTo

To ensure that an employee is not assigned to more than one office, add a unique index to the Offices.[AssignedTo] field. Regardless of whether there is no relationship, a one-to-many relationship, or a one-to-one relationship defined between these tables, Microsoft Access will determine that the relationship is one-to-one when determining whether to perform an AutoLookup query.

Steps to Reproduce Behavior
  Open the sample database Northwind.mdb (or NWIND.MDB in version 2.0) and create the following new table:

      Table:  Offices --      FieldName: OfficeID Data Type: AutoNumber Field Size: Long Integer New Values: Increment FieldName: Building Data Type: Text FieldName: AssignedTo Data Type: Number FieldSize: Long Integer DefaultValue:  Select the OfficeID field, and then click Primary Key on the Edit menu.  View the table in Datasheet view, and then add the following data to the table:

      OfficeID   Building   AssignedTo --          1          A           2          A           3          B                        </li> Create a new query based on the Employees and Offices tables.</li> Join the tables on the Employees.[EmployeeID] and Offices.[AssignedTo] fields.</li> Drag all the fields from the Offices field list to the query grid, and then drag the FirstName and LastName fields from the Employees field list to the query grid.</li> Run the query. Type 7 in the AssignedTo field, and then press ENTER. Note that the AutoLookup query fills in the FirstName and LastName fields for the record.</li> Save the query as AssignOffices, and then close it.</li> Open the Offices table in Design view.</li> Set the AssignedTo field's Indexed property to Yes (No Duplicates).</li> Save the table and close it.</li> Run the AssignOffices query. Type 3 in the first blank AssignedTo field and press ENTER. Note that Microsoft Access does not fill in the FirstName and LastName fields.</li> Press SHIFT+F9 to requery. Note that the fields are filled.</li></ol>

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