SQL Server useful but less known features

Michał Turecki — Wed, 02 Nov 2016 11:43:56 +0000

Checking who is connected to the database

sp_who

SELECT NULL as [Connections by Database], [host_name] AS [Client Machine], db.name AS [Database], [program_name] AS [Client Program], COUNT(*) AS [Open Connections] FROM sys.dm_exec_sessions s (nolock) LEFT JOIN sys.dm_exec_requests r (nolock) ON r.session_id = s.session_id LEFT JOIN sys.databases db (nolock) ON db.database_id = r.database_id WHERE s.session_id >= 50 -- Ignore SQL Server processes GROUP BY [host_name], db.name, [program_name] ORDER BY [Client Machine], [Database], [Client Program]
Adjusting connection pooling settings

By default pool size is 100 per database with a command timeout (effectively a connection timeout) of 15 seconds. To increase add following to the connection string:

Connection Timeout=30;Pooling='true';Max Pool Size=200
Checking the size of column's contents

To check how much data the column contains:

SELECT *, DATALENGTH([column]) AS ColumnSizeInBytes FROM table
Using SQL Server profiler

Profiler is a powerful way to debug application performance problems, to check query execution time. If you're developing any application using SQL Server as a database, running it at least once for every application release can help with pinpointing possible performance issues. Remember the rule - there should be a constant number of queries regardless of the amount of records fetched - that way application will scale better. Sometimes it's better to replace a single complex query with more simpler queries because for each result row, columns shared by joins are repeated and delivered to client for processing many times.

How to save data from all tables in SQL Server database into CSV files (using PowerShell)

Michał Turecki — Wed, 23 Sep 2015 09:24:44 +0000

All it takes is to create the following PowerShell script (text file with .ps1 extension) and changing $server and $db variables to match the server's host and instance name (SERVER\INSTANCE) and a database name.

$destDir = Get-Location
$server = "localhost"
$db = "DatabaseToExport"

Import-Module -Name SQLPS
$tables = Invoke-Sqlcmd -query "SELECT name FROM sys.tables" -Database "$db" -ServerInstance "$server"
foreach ($table in $tables)
{
	$tableName = $table["name"]
	write-host -ForegroundColor Green "Creating File $tableName.csv"
	Invoke-Sqlcmd -Query "SELECT * FROM $tableName;" -Database "$db" -Server "$server" |
		Export-Csv -NoTypeInformation -Path "$destDir\$tableName.csv" -Encoding UTF8
}

Michał Turecki - sql-server

SQL Server useful but less known features

Checking who is connected to the database

Adjusting connection pooling settings

Checking the size of column's contents

Using SQL Server profiler

How to save data from all tables in SQL Server database into CSV files (using PowerShell)