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archanasql
Starting Member
27 Posts |
 Posted - 2008-02-08 : 13:55:37
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| Hi,Can a foreing key ever contain null values and if so how many null values can it contain? and how can a foreign key contain null values when we have a referential integrity in referenced table with the Primary key which cannot contain null values? i am totally confused..? Please clarify? |
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hali14
Starting Member
5 Posts |
Posted - 2008-02-08 : 14:02:14
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| No |
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TG
Master Smack Fu Yak Hacker
6065 Posts |
Posted - 2008-02-08 : 14:04:30
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| A foreign key constraint exists only to prevent values that don't exist in the <foreign> table. The nullability property of the column determines if nulls are allowed. So a Nullable column that references another table.column can contain unlimited nulls. On the other hand if you want to insure that every row is accounted for (no nulls) then make the column NOT NULL.Be One with the OptimizerTG |
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can a foreign key contain nulls?