[AccessD] Very interesting quirk in table design...

Gary Kjos garykjos at hotmail.com
Tue May 13 21:32:34 CDT 2003


Cool shortcut to save an update query to initialize a new field. I'll have 
to try that sometime.

Gary Kjos
garykjos at hotmail.com





>From: Drew Wutka <DWUTKA at marlow.com>
>Reply-To: accessd at databaseadvisors.com
>To: "'AccessD at databaseadvisors.com'" <AccessD at databaseadvisors.com>
>Subject: [AccessD] Very interesting quirk in table design...
>Date: Tue, 13 May 2003 19:42:55 -0500
>
>I just noticed something tonight.  I had to go into an existing table and
>add a few fields.  One field was numeric, then I was going to add two 
>Yes/No
>fields.  I did this.  The numeric field was blank/null for all existing
>records.  However, I wanted a Yes/No/Not Answered for the Yes/No fields, so
>I dropped one of them, and changed the other one to a byte number (1-yes,
>2-no, 4-Yes, 8-No) which will let me know the answer for both and whether
>they were answered at all.  When I looked back at the datasheet view, the
>byte field (which was a yes/no) was all 0's, and the number field was still
>all blank.
>
>So I hypothesized that by setting a Yes/No field, you had either 0 or -1
>(maybe 1, I don't remember), but since a Yes/No field only has two possible
>values, there was nothing for null, so each field is automatically 
>populated
>with 0 or -1.  By switching that field to a number field, it tried to
>'convert' the data in those fields, which it did successfully to 0.
>
>So to prove this, I went into design for that table, changed my 'null
>filled' number field to Yes/No, hit save, changed it back to number, and 
>hit
>save again.  Whalla, went into datasheet view, and no I had all zero's in 
>my
>number field.
>
>Pretty interesting eh?  (Or do I just need some sleep?)
>
>Drew
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