Slow distinct query in SQL Server over large dataset

Question

We\'re using SQL Server 2005 to track a fair amount of constantly incoming data (5-15 updates per second). We noticed after it has been in production for a couple months that on

Answer 1

I doubt SQL Server will even try to use the index, it'd have to do practically the same amount of work (given the narrow table), reading all 200M rows regardless of whether it looks at the table or the index. If the index on typeName was clustered it may reduce the time taken as it shouldn't need to sort before grouping.

If the cardinality of your types is low, how about maintaining a summary table which holds the list of distinct type values? A trigger on insert/update of the main table would do a check on the summary table and insert a new record when a new type is found.