Evaluate and comment on the following general statement:
In a well designed database, the clustered index should never be on the primary key.
The point being that the normal use case isn't "I know the primary key and need to find the rest of the columns", but instead "I know data in 3 columns, show me all the records that match so I can find related data using the PK elsewhere in the database".
I think that this is the single biggest performance blunder done by programmers and n00b dba's. It's also incredibly inconvenient to fix, requiring a lot of locking and...