CODEWITHSUNDEEP
ms-accessrelationshiplookup-tables
N.Barrett
N.Barrett

Reputation: 61

Access changes table Relationships by itself

I am struggling with an issue in designing my Access database.

I am a caregiver, and part of my job is taking clients out into the community. I am attempting to build a catalog of outings to help the employees at our company come up with and store ideas for these. I want to store information for each of up to 5 types of events that clients can do at a location. That information includes the event type, when it runs and doesn't, and how much it'll cost, all of which would be user-selectable. (Separately in the same table, I want to include contact information and information that helps the user search for event locations, such as the ZIP code.) I have attempted to normalize the database by spreading event information across fields in the main table, linked to lookup tables. I am aware that Access has a limit of 32 relationships per table.

To help staff find event types, I am trying to set up a method for categorizing them. That requires setting up nested lookup tables, as shown in the first picture. If I understand correctly, the additional "copies" of those lookup tables are aliases. When I save the setup for the relationships between those aliased lookup tables, close the Relationships window, and open it again, I find Access has changed them, as shown in the second picture. This happens whether I delete the lookup table information for each field in Datasheet View. I don't understand why it does this or how to fix it.

Upvotes: 0

Views: 293

Answers (1)

Gord Thompson
Gord Thompson

Reputation: 123594

To answer your question:

In the object browser I see that you have only one table: t_OutingType. Therefore, the "tables" t_OutingType_2, t_OutingType_3 are just aliases; "pointers" to the same table (like a shortcut to a document). When you save the relationships and close the window, the relationship information is written to the metadata of the database. When you re-open the Relationships window Access re-builds the relationship diagram from the metadata, and it does not include the redundant aliases.

Additional advice:

Whenever you find yourself duplicating columns in a table, e.g., Event_1, Event_2, ... a little voice in your head should start shouting "Are you sure that's a good idea?" Imagine if you want to search the database for events that fall on a certain date. With the table layout described above you would need to ...

SELECT ... WHERE EventDate_1 = [theDate] OR EventDate_2 = [theDate] OR EventDate_3 = [theDate] ...

It's almost always better to split the Event information into a separate child table and maintain an association table between the child table and its parent.

Upvotes: 2

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