Explain ‘Null Values’ and ‘Complex Attributes’.

1.	Explain ‘Null Values’ and ‘Complex Attributes’.
Answer» Null Values: Absence of data item is represented by a special value called null value. There are three situations which may require the use of null value. When particular attribute does not apply to an entity. Value of an attribute is unknown although it exist. Unknown because it does not exist. Complex Attributes : These are composite and multivalue attributes which may be nested (or grouped) to constitute complex ones. The parenthesis { } are used for showing grouping of components of composite attributes. The braces { } are used for showing the multivalue attributes.

Answer»

Null Values: Absence of data item is represented by a special value called null value. There are three situations which may require the use of null value.

When particular attribute does not apply to an entity.
Value of an attribute is unknown although it exist.
Unknown because it does not exist.

Complex Attributes : These are composite and multivalue attributes which may be nested (or grouped) to constitute complex ones. The parenthesis { } are used for showing grouping of components of composite attributes. The braces { } are used for showing the multivalue attributes.

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Explain ‘Null Values’ and ‘Complex Attributes’.

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