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> Are "extended Datatypes" Just Look-up Fields., Access 2016    
post Jun 15 2018, 11:04 AM

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Joined: 3-May 17
From: France

I was looking at datatypes, and I came across a list of "Extended datatypes" here:

Are they in fact just the look-up fields that I have so often read that I should avoid?
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Doug Steele
post Jun 15 2018, 12:04 PM

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From: St. Catharines, ON (Canada)

No, extended fields have nothing to do with lookup fields.

The article does a reasonable good job of explaining how they're simply modifications to existing data types.
These 5 data types take an existing base data type and add a behavior to it. Two of the AutoNumber types take a normal 32 bit integer field and add an auto-populating behavior, while the AutoNumber GUID type does the same with a normal GUID field. The Hyperlink field is really just a memo (long text) field with a flag that the user interface uses to format the contents as a hyperlink. Finally, calculated fields can be of any non-binary type. They become “calculated” fields by assigning an expression. These steps are reversed in the table designer, where first you select the “Calculated” field type and then choose the “Result Type”.

I suppose an argument could be made against using calculated fields, but they're really fairly benign.
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post Jun 15 2018, 12:13 PM

Posts: 385
Joined: 3-May 17
From: France

Sorry, Doug, I got my question wrong. What I meant was "Are Complex data-types just look-up fields?"
After more research, I guess I meant "Are Complex data-types just multi-column look-up fields?"

If they are, do they just make "the evils of lookup fields" even more evil? I have picked a side on the "look-up" field controversy, which is : "better safe than sorry".
This post has been edited by Jaiket: Jun 15 2018, 12:16 PM
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post Jun 15 2018, 03:57 PM

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From: LI, NY

The article explains them as Attachment fields as well. Basically what they do is simulate a separate table contained in a field. They allow you to select multiple items as part of a single field.

I'm not a fan of them. I would prefer to use a separate table and control it myself.
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