Unique index behavior question

Let's say a table has a column, call it A, that has a unique index on it.

Client 1 and client 2 start transactions. Client 1 adds or updates a row in the table with a particular value for column A. Then, client 2 tries to add or update a different row using the same value for column A, and does so before client 1 commits its transaction.

Will client 2 receive an immediate error when it attempts to make its change, or will the error occur when the clients commit their transactions? Will the last client that commits receive the error, or the last client to perform the update? Received on Fri Mar 23 2001 - 11:46:18 CST