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In a database management system, what are the two integrity rules? |
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Answer» REFERENTIAL integrity rules and ENTITY integrity rules are the TWO forms of integrity rules. According to referential integrity requirements, if a primary key value is used as a foreign key in a child table, it cannot be changed. Let R and S be two different relations. Assume that R relates to the relation S through a set of attributes that serve as the Primary Key of S and as a Foreign Key in the relation R. The Foreign Key in a TUPLE in R must then be either equal to the Primary Key in a tuple in S or completely NULL. The main key value cannot be null due to entity integrity. An attribute X of a relation R(R) cannot take null values if it is a PRIME Attribute of R(R). A Prime Attribute is an attribute that is a part of a relation's Candidate Key. |
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