Use lightweight query profiling to inspect live operator rows and in-flight plans, while avoiding misleading progress percentages.
SQL SERVER – Parameter Sniffing Simplest Example
Today we will see a very simple example of the Parameter Sniffing. Let us see a very simple example of the parameter sniffing.
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.
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.
Row Mode Memory Grant Feedback: It Needs Level 150
Row mode memory grant feedback needs compatibility level 150 or higher, while batch mode needs only 140. A tested demo runs a row mode sort and a batch mode sort at levels 140, 150 and 170. The row sort keeps its grant of 11,888 KB at level 140 and drops to 1,536 KB at 150.