I remember one of the most surprising changes in SQL Server 2000 2005 was how the graphical plans showed the use of a nonclustered index to seek, and the plan included something that looked like a JOIN to find rows in the base table.  Here’s an example. Although I used SQL Server 2008R2, the graphical plan will be pretty similar to what it ...

I wrote about ''Too Many Columns'' last September, and along with changes in SQL Server 2008 that allow lots of columns, there is also the ability to create more than the old maximum of 249 nonclustered indexes on a table. I knew this fact, but somehow I overlooked it when updating the chapter on table structures in my new book. My omission also ...

Most of you are probably aware that having a clustered index on the column(s) in an ORDER BY clause means that SQL Server can avoid having to sort your data, because it is already logically stored in order of the clustered index, and SQL Server can just access the data in order to get the sorted data . For example, consider the SalesOrderHeader ...

If you’ve ever run DBCC SHOW_STATISTICS,  you know you get 3 sections of information back. The first section is basic information about the last time the statistics were updated, the number of rows, the number of steps, etc. The second section is density information for each left-based subset of columns. The third section is the histogram for ...

  Hopefully, if you know enough about SQL Server to understand most of my posts here, you're aware of the fact that using a nonclustered index is not always an optimal choice for accessing data, particularly if there are thousands (or more) rows of data you need to retrieve.  However, we should never say 'never'. ...