In a SQL Server Execution plan what is the difference between an Index Scan and an Index Seek
I'm on SQL Server 2005.
An index scan is where SQL server reads the whole of the index looking for matches - the time this takes is proportional to the size of the index.
An index seek is where SQL server uses the b-tree structure of the index to seek directly to matching records (see http://mattfleming.com/node/192 for an idea on how this works) - time taken is only proportional to the number of matching records.