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Trying to update a table with foreign keys causes a key violation error.

Posted on 2008-06-11
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Last Modified: 2011-10-19
I am trying to update a table wihch has a single Primary key and a number of foreign key fields - the foreign key fields have properties of:  Required = No, Indexed = Yes (Duplicates OK) and Default value = NULL. When I try to UPDATE this table supplying the primary key and one or several of the foreign keys I get a Key violation error. If the FKs allow nulls, I am bemused why this should occur ? Any ideas anyone ?
The PK I am supplying id definitly unique.
If I dont supply any of the FKs I dont get a key violation and the table updates.
I am enforcing referential integrity between the primary and foreign key tables.

Tony
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Question by:fester62
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Assisted Solution

by:DatabaseMX (Joe Anderson - Access MVP)
DatabaseMX (Joe Anderson - Access MVP) earned 50 total points
Comment Utility
Remove NULL as the 'Default Value'
By definition - they will be Null unless you populate them

Also ... are you *sure* that you have INexed = Yes (Duplicates OK) for all FK's ?

mx
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Assisted Solution

by:Mark Wills
Mark Wills earned 180 total points
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There is a reasonable probability that the columns being supplied are not NULL, they may well be an empty string, or zero length string which is not the same as NULL and will try to populate. That is the typical reason when it works if you do not supply the column. So, check those columns, and make sure they are in fact NULL.
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Author Comment

by:fester62
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MX: yes all FK fields are set to Yes(Duplicates OK) in primary table; I have re-checked.

Tony
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Author Comment

by:fester62
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mark_wills: I am only supplying non-null values at present, so there is no opportunity for getting "" mixed up with NULLs. I am aware of the difference.

I have tried a number of INSERTS using different combinations of the fields in the Primary table (there are some 30 odd altogether). At present it seems to fail on one particular field, that happens to be called 'OU Code'. The INSERT statement is as follows:

INSERT INTO tblResources ([GPN], [FirstName], [LastName], [FTE], [PAC], [OUCode], [DataSource]) VALUES ('HRID11112', 'test 1', 'test 2', 1, 1, 'GUBY', 'M');

The field has the properties in the update table and Related table as shown in the attached.

tony



OU-Code-properties.bmp
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Author Comment

by:fester62
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Btw, I have tried the above statement omitting the OU Code and it is successful, so it cannot be due to any other field. I have a similar problem with other FK Fields (not included in the above INSERT), but they are all defined in a similar way to the above.

Tony
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Author Comment

by:fester62
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Attached relatonship definition:
OU-Code-relationship.bmp
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Expert Comment

by:Mark Wills
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Hi tony,  Good detective work... cannot see anything untoward, you have allow zero length, and it is not required... You wouldnt happen to have a test database or something that does not compromise security / IP etc that you would care to share ?
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Accepted Solution

by:
fester62 earned 0 total points
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I think I may have just figured the problem...and the clue is in the above! I have another table called OUstructures which defines a hierarchy of OU Codes. However, the primary table for OU Codes in tblOUCodes and any validation of OU Codes should always be done against this. For some reason, although whilst doing some work in the relationships window, I managed to invert the relationship between OUStructures and OUCodes, so that OUStructures became the Primary table.

In another case I set a default of '0' for a numeric key on the many side but did not allow this as a default value in the primary table.

Tony


Tony
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Author Comment

by:fester62
Comment Utility
Thanks for your comments, often just posting stuff here makes you go through and retest things you thought you had made good, but sometimes havent!

Part of the solutuion was prompted by mark_wills comments re: checking what values, nulls, "" etc are being supplied, so I will award half the points there. The rest nobody could have figured out until I posted the last screenshot. Thx Mark.

Tony
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