To index a computed column, define the formula once on the table and create a normal index on it. This post loads 200,000 rows, shows the scan, then the seek after the index, and tests the rules that decide whether SQL Server accepts the column.
Reading the Connectivity Ring Buffer for Dropped Connections
The error log says nothing, but the connectivity ring buffer may remember. Here is how to read it and what it cannot tell you.
Status Changes Only: Collapsing Repeated Rows With LAG
Hundreds of repeated readings, three real changes. Here is how LAG finds them, and why a plain not-equal test quietly drops rows.
Latch Waits at the Top: Reading sys.dm_os_latch_stats
Sample SQL Server latch waits by class, then connect ACCESS_METHODS_DATASET_PARENT, FGCB_ADD_REMOVE, and LOG_MANAGER to the next check.
Group by Query Hash: Find One Query With Many Plans
Group by query hash to add up every cached copy of one query. See why the top query hides across entries in SQL Server.
One Query Many Plans – SQL in Sixty Seconds #171
After the blog post, lots of people asked me it will be more helpful if I can create a video on the same topic of one query many plans.
Read-Ahead Reads in STATISTICS IO: What They Tell You
Interpret read-ahead reads in STATISTICS IO, compare isolated cold scans and seeks, and separate prefetch from storage-wait evidence.