What is the difference between UNIQUE KEY and UNIQUE INDEX?
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Answer Posted / 1
There is a clear difference between the 2. A unique
constraint defines what combination of columns has to be
unique. A unique index is just a way of making sure the
above is always valid. But it's possible to have a non-
unique index supporting a unique constraint. (if the
constraint is deferable = Only has to be valid at commit
time but is allowed to be broken in the middle of a
transaction)
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