NOCOUNT performance depends on the messages that SQL Server no longer sends to the client. This post counts the network packets of a procedure with a 5,000 step loop, with the setting off and on. It also explains why some tests show no time gain, and where the setting helps most.
Copy Database Without Statistics and Query Store Data
To copy database without statistics, add NO_STATISTICS and NO_QUERYSTORE to DBCC CLONEDATABASE. This post shows why that matters, because histograms and Query Store texts hold real values. It also shows the plan estimate that changes, how to make a clone writable, and what VERIFY_CLONEDB does.
Skipping No-Op Updates: Changing Only Rows That Really Differ
Skip no-op updates with NULL-safe EXCEPT or IS DISTINCT FROM, inspect affected counts, and avoid unnecessary rowversion and trigger changes.
Clone Database in SQL Server With DBCC CLONEDATABASE
Clone Database in SQL Server with DBCC CLONEDATABASE and you copy the structure and the statistics without a single row. This post runs the command on a demo database, checks what the clone holds and what it leaves out, and shows that the optimizer builds the same plan from the copied statistics.
Why Execution Plan Operator Read More Rows Than Available? – Interview Question of the Week #255
Question: Why Execution Plan Operator Read More Rows Than Available?
Answer: Statistics.
Now let us learn detailed answer in this blog post.
Query Plan Join: Why a Query With No Join Shows One
A query plan join can appear even when the query has no join, because SQL Server joins a nonclustered index to the table itself. This post reads the plan of a one table query, removes the join with a covering index, and finds the row count where SQL Server stops using lookups.
Statistics Sample Percent and PERSIST_SAMPLE_PERCENT
The statistics sample percent decides how many rows SQL Server reads when it updates a statistic. A tested demo on 1,000,000 rows shows the default sample of 35.5 percent, a FULLSCAN of 100 percent, and the way PERSIST_SAMPLE_PERCENT keeps 100 percent for later updates, including an automatic one. It also shows that a sampled update can be slower than a full scan.