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Sunkist
Starting Member
4 Posts |
 Posted - 2008-06-08 : 04:28:51
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| I am creating a series of foreign keys in my new database, and so far everything is going fine. The company I work for never uses them, and I am working on my own stuff on my own time now. I come across one table that I do want one field to allow zeroes, but when its set to a value, to exist in the other table.To be more specific. I have a PO type table, which has an EmployeeID of the person who made the PO, and another field to store who received the PO when the order arrives. I want that 2nd Employee field to be zero until it's received. I created an employee of zero, to allow the foreign key to be created. But all the other tables that have foreign keys to my Employee table I would prefer to not allow zeroes. So I changed them to use a check of (employeeid > 0).Is it possible to have a foreign key say that I want the value from the Field in Table A to exist in table B, or to be zero? Or would it just be easier to leave off the foreign key in this one case?Tks |
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rmiao
Master Smack Fu Yak Hacker
7266 Posts |
Posted - 2008-06-08 : 14:36:18
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| Fkey column can have any value as along as column in parent table has that value. |
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Sunkist
Starting Member
4 Posts |
Posted - 2008-06-08 : 15:03:17
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| I didn't originally want to add EmployeeID zero to my Employee table however. I did yesterday in order to create this foreign key, but was wondering if I could still create a foreign key without creating a record for Emp # zero? |
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jezemine
Master Smack Fu Yak Hacker
2886 Posts |
Posted - 2008-06-08 : 15:47:27
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if the FK is nullable, it can also be NULL (even though the PK column can nerver be NULL)
elsasoft.org |
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Sunkist
Starting Member
4 Posts |
Posted - 2008-06-08 : 16:17:35
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| Thanks jezemine, I will give that a try. :) |
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Foreign Keys - Allow zero?