The heap or clustered index choice changes the reads of every scan. The demos measure forwarded records in a heap, a range query on both kinds of table, and the size of a nonclustered index on a wide key, and says when a heap is the right choice.
Count Rows in a Heap: Which Scan Does SQL Server Use?
Count rows in a heap and SQL Server scans every page. See the plan change with a clustered and a narrow index, and why a heap does not compact its pages.
Forwarded Records and Performance – SQL in Sixty Seconds #155
Forwarded records make SQL Server read extra pages when it scans a heap. In this SQL in Sixty Seconds video, I explain forwarded records and performance.
SQL SERVER – Finding Fragmentation in Forwarded Records
Finding Fragmentation in a heap also requires a separate check for forwarded records. I measure their effect before choosing maintenance.
SQL SERVER – Heaps, Scans and RID Lookup
The question was do heaps are very bad and always force a table scan? Let us learn about RID Lookup, Heaps and table scan.
RID Lookups on Heaps vs Key Lookups on Clustered Tables
Compare RID lookups on heaps with clustered key lookups, inspect forwarded records, and test covering indexes with actual plans and reads.
SQL SERVER – Parallelism for Heap Scan
Two DBAs asked me if their table needed a clustered index. Our conversation during a Health Check turned into a lesson on parallelism for Heap Scan.