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Primary key vs. unique key

Kent Milligan EXPERT RESPONSE FROM: Kent Milligan

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QUESTION POSED ON: 11 July 2003
What is the difference between a primary key and a unique key in DB2?


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One difference is that a unique key constraint can be created over columns with null values, while a primary key constraint does not allow null values. The other difference is that there can only be one primary key constraint defined on a table, but there can be multiple unique key constraints defined on a table.

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