The DBCC SHOW_STATISTICS command gives us detailed information about the statistics and dataĭistributions. So that, optimizer estimates how much memory and other resources are required for a query So we can list all tables of a SQL Server database, identifying the size to each table we need to run something other than a COUNT method on SELECT statement. When we create an index this data distribution information is also stored for the NULL valued columns. “How does the SQL Server query optimizer know how many NULL rows are stored for a column in a table?”īasically, the statistics store the data distribution about the tables, and the query optimizer makes use of this information during the creation of a query plan. Most likely, the following question will pop up in your mind.
This situation shows that the query optimizer finds accurate information about how many NULL rows are stored in the tables DB.execute ('select from sqlitemaster where type like table') for tablerow in tables: tableName tablerow 2 print ('tableName ' + tableName) columns DB. To show tables in a database using the sqlite command line shell program, you follow these steps: First, open the database that you want to show the tables: > sqlite3 c:sqlitedbchinook.
The index seek operator details show us there is not any difference between the Actual Number of Rows and the Estimated Number of Rows. Without a doubt, the created index is used by the database engine and it boosts the performance of the query because the logical reads number is lower than the previous one. There are two ways to obtain this information: Using system tables with Transact-SQL (T-SQL) Querying the 'Tables' folder on 'Object Explorer Details' panel We will demonstrate how these features can be used.