* A PRIMARY KEY is a unique KEY where all key columns must be defined as NOT NULL.
KEY is a synonym for INDEX. So, specifying PRIMARY KEY implies UNIQUE and INDEX.. You don't have to specify them yourself.
At 01:11 am 4/11/2004, you wrote:
I learned that there are three types of indexes (PRIMARY, UNIQUE, and INDEX).
Now assuming I create a performance-critical PRIMARY key, will I better have to specify UNIQUE and INDEX for this column also !? It should be obvious that a primary key is unique anyway, and an index as well, shouldnt it !? Please note, I am not after saving disk space here, performance is all I am after, and such a three-fold indexing exercise just seems redundant to me in the best case scenario, or harmful even, am I right there !?
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