Creating Relationship vs Selecting Raw Source (1 Viewer)
- Thread starter Jonny
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isladogs
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The purpose of creating relationships is to impose referential integrity between tables.
See http://www.mendipdatasystems.co.uk/relationships1/4594533224
Don't understand your reference to a field raw source.
See http://www.mendipdatasystems.co.uk/relationships1/4594533224
Don't understand your reference to a field raw source.
By field raw source I mean to SQL code to populate the combobox (or any other control).
Sorry If my question sounds stupid.. but..
When I build a form I bound all fields to various tables, where comboboxes are populated from tables and table are updated from text fields.
In that way I've managed to create a project without creating relationships between tables.
Therefore I do not really understand the purpose of table relationships?
Sorry If my question sounds stupid.. but..
When I build a form I bound all fields to various tables, where comboboxes are populated from tables and table are updated from text fields.
In that way I've managed to create a project without creating relationships between tables.
Therefore I do not really understand the purpose of table relationships?
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Hi Jonny. See if this old article on using the Lookup tab helps explain some things.
Lightwave
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Referential integrity WILL CATEGORICALLY enforce the relationship between tables across all forms. It also automatically sets up the correct relationship when creating queries.
Lookup tables on forms MAY IF SET CORRECT enforce the relationship between tables and will have to be set correctly on every form the field is shown. When writing queries you will need to set the relationship each time as well which you could get wrong.
Therefore if you have many forms which show the same information it is easier to ensure that all your forms are correct.
But yes you can do it either way but there is more rigor to the former method.
There are systems where referential integrity is VERY important. EG an athlete racing system whereby individuals are allocated race bibs. These bibs exist as paper and are given to each competitor. If you enter a ficticious number in the database problems cascade as a volunteer can't give them the actual race number and a whole load of things start happening... Typically the volunteer draws a new number or gives the next number. Person is then recorded against that number. But he's not in the database against that number so might not have his time recorded.
Lookup tables on forms MAY IF SET CORRECT enforce the relationship between tables and will have to be set correctly on every form the field is shown. When writing queries you will need to set the relationship each time as well which you could get wrong.
Therefore if you have many forms which show the same information it is easier to ensure that all your forms are correct.
But yes you can do it either way but there is more rigor to the former method.
There are systems where referential integrity is VERY important. EG an athlete racing system whereby individuals are allocated race bibs. These bibs exist as paper and are given to each competitor. If you enter a ficticious number in the database problems cascade as a volunteer can't give them the actual race number and a whole load of things start happening... Typically the volunteer draws a new number or gives the next number. Person is then recorded against that number. But he's not in the database against that number so might not have his time recorded.
Thank you , guys , for a comprehensive explanation. While trying to move the existing DB from look-up tables to referential integrity I encountered errors in comboboxes:
Looks as the problem that I'm trying to create a structure on existing database..
However using referential integrity + Combo Box Wizard looks as the right combination to do that.
Looks as the problem that I'm trying to create a structure on existing database..
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That's because the Wizard asks you if you want to "hide" the ID column.
So why when I'm hiding it without the wizard I'm getting an error?
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Hi. You'll have to show us exactly what you did before we can have an idea of the "why." Are you able to post a screenshot or sample db?
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Hi. Thanks for posting a sample, it helps understand the problem a lot. I can see two problems with your first combobox.
1. The Row Source is different from the second combobox, and
2. The Column Count and Column Widths are also different
Another problem I see with your database is you're using a Lookup field in the Employee table for the Department. This is adding to the confusion.
Eureka,
The main problem in all my combos was "not-applying" 0cm width for a first column!!
Thanks so much!
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Hi. You're welcome. We're all happy to assist. Good luck with your project.
