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BOOK: Beginning MySQL
This is the forum to discuss the Wrox book Beginning MySQL by Robert Sheldon, Geoff Moes; ISBN: 9780764579509
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Old April 7th, 2009, 05:43 AM
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Cool DUPLICATE VALUES ?

que. is regarding mysql5.1

what is meant for DUPLICATE VALUES in Index (viz.unique, regular)
thx !
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Old June 7th, 2010, 06:15 PM
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An index contains duplicate values, when at least one value occurs more than once in the index (and hence, in the column being indexed).

For an index defined on more than one column, an index value is considered duplicate only if all indexed fields of two or more rows of the table are completely identical.

A "unique" index disallows duplicate values. Disallowing duplicate values in a table column can only be enforced by creating a unique index on that column.

-- Peter.
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