Composite primary key

Hello,

Does composite primary key affect performance on the table that contains the composite primary key or tables that references this table?

When composite primary key should be used?

In my experience composite keys are a through back to old systems that where converted to databases such as SQL Server / Oracle.

As a developer, rather than a DBA, composite keys are a real pain to program against especially in the modern world of object programming, data objects etc. I would always use a single unique value to identify a row rather than using composite keys. If you regularly query dataing using mulitple values from columns in the where statement then by all means create a normal index based on these columns (in the order that you use them in the where statement).

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so considering performance issue!! does databases with such structure perform worse than ones with single keys!! i mean directly or indirectly.

*Directly: if it has a bad performance in join clauses or in search criteria.

*Indirectly: in programming specially in .Net when using datagrids and such controls that generate relations and act with whole tables in runtime.

Thnx