Question:How is a "no changes" constraint implemented for an attribute?
Answer The no change (NC) concept allows the database designer to prohibit changes to the values in a column. This concept is used mainly for columns participating in primary keys. Preventing changes to a primary key is recommended because primary keys are used to create relationship between tables, and changes to a primary key could result in a referential integrity violation.
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How is a "no changes" constraint implemented for an attribute?