When using indexes is it ok to index a field by itself (and allow duplicates) and then use it as part of a multi field index which doesn't allow duplicates.
For example. I have Employee Number, First Name and Last name fields in a table. If I index them separately allowing duplicates in the name fields but then index all three fields together so that I don't end up with more than one entry for the same employee is that OK or do I even need to index the fields individually at that point?