COMPUTER SCIENCE AND ENGINEERING
SQL
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Which is the statement which is not correct about Foreign Key?
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It is a primary key of another table
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The description of the column should be same
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There can be multiple foreign keys in a table
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It supports null values
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Explanation:
Detailed explanation-1: -Q 26-Which of the following is not true about a FOREIGN KEY constraint? A-It is a referential integrity constraint.
Detailed explanation-2: -Foreign keys allow key values that are all NULL, even if there are no matching PRIMARY or UNIQUE keys.
Detailed explanation-3: -The above statement is wrong. A foreign key column must not contain unique values. A FOREIGN KEY constraint can contain null values; however, if any column of a composite FOREIGN KEY constraint contains null values, verification of all values that make up the FOREIGN KEY constraint is skipped.
Detailed explanation-4: -A foreign key may not be null when it is part of a composite primary key in the child table.
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