How to Find the Data Directory for a SQL Server Instance

How do I find the data directory for a SQL Server instance?

It depends on whether default path is set for data and log files or not.

If the path is set explicitly at Properties => Database Settings => Database default locations then SQL server stores it at Software\Microsoft\MSSQLServer\MSSQLServer in DefaultData and DefaultLog values.

However, if these parameters aren't set explicitly, SQL server uses Data and Log paths of master database.

Bellow is the script that covers both cases. This is simplified version of the query that SQL Management Studio runs.

Also, note that I use xp_instance_regread instead of xp_regread, so this script will work for any instance, default or named.

declare @DefaultData nvarchar(512)
exec master.dbo.xp_instance_regread N'HKEY_LOCAL_MACHINE', N'Software\Microsoft\MSSQLServer\MSSQLServer', N'DefaultData', @DefaultData output

declare @DefaultLog nvarchar(512)
exec master.dbo.xp_instance_regread N'HKEY_LOCAL_MACHINE', N'Software\Microsoft\MSSQLServer\MSSQLServer', N'DefaultLog', @DefaultLog output

declare @DefaultBackup nvarchar(512)
exec master.dbo.xp_instance_regread N'HKEY_LOCAL_MACHINE', N'Software\Microsoft\MSSQLServer\MSSQLServer', N'BackupDirectory', @DefaultBackup output

declare @MasterData nvarchar(512)
exec master.dbo.xp_instance_regread N'HKEY_LOCAL_MACHINE', N'Software\Microsoft\MSSQLServer\MSSQLServer\Parameters', N'SqlArg0', @MasterData output
select @MasterData=substring(@MasterData, 3, 255)
select @MasterData=substring(@MasterData, 1, len(@MasterData) - charindex('\', reverse(@MasterData)))

declare @MasterLog nvarchar(512)
exec master.dbo.xp_instance_regread N'HKEY_LOCAL_MACHINE', N'Software\Microsoft\MSSQLServer\MSSQLServer\Parameters', N'SqlArg2', @MasterLog output
select @MasterLog=substring(@MasterLog, 3, 255)
select @MasterLog=substring(@MasterLog, 1, len(@MasterLog) - charindex('\', reverse(@MasterLog)))

select 
    isnull(@DefaultData, @MasterData) DefaultData, 
    isnull(@DefaultLog, @MasterLog) DefaultLog,
    isnull(@DefaultBackup, @MasterLog) DefaultBackup

You can achieve the same result by using SMO. Bellow is C# sample, but you can use any other .NET language or PowerShell.

using (var connection = new SqlConnection("Data Source=.;Integrated Security=SSPI"))
{
    var serverConnection = new ServerConnection(connection);
    var server = new Server(serverConnection);
    var defaultDataPath = string.IsNullOrEmpty(server.Settings.DefaultFile) ? server.MasterDBPath : server.Settings.DefaultFile;
    var defaultLogPath = string.IsNullOrEmpty(server.Settings.DefaultLog) ? server.MasterDBLogPath : server.Settings.DefaultLog;
}

It is so much simpler in SQL Server 2012 and above, assuming you have default paths set (which is probably always a right thing to do):

select 
    InstanceDefaultDataPath = serverproperty('InstanceDefaultDataPath'),
    InstanceDefaultLogPath = serverproperty('InstanceDefaultLogPath')

MS SQL Server Docker data location

The files, for SQL Server on Linux, are by default located in /var/opt/mssql. Unsurprising the Data files are in the data directory, and the log files in the log directory.

This is also in the documentation Change the default data or log directory location:

The filelocation.defaultdatadir and filelocation.defaultlogdir settings change the location where the new database and log files are created. By default, this location is /var/opt/mssql/data.

changing default data directory for sql server after installation

This is to let you know the solution to my problem. I have successfully changed the data root directory by moving the data and log files for all the system DBs to the desired location.I also had to change the registry value for the SQLDataRoot directory to my desired location and modify the location of the server diagnostics file as per my cluster requirement. After all this, I have been able to successfully move the folder to the desired location. Thanks for all the help everyone.

How is location of |Data Directory| in connection strings resolved?

Here is the code which specifies where is |DataDirectory|

GetDataDirectory

[PermissionSet(SecurityAction.Assert, Unrestricted = true)]
internal static string GetDataDirectory() {
    if (HostingEnvironment.IsHosted)
        return Path.Combine(HttpRuntime.AppDomainAppPath, HttpRuntime.DataDirectoryName);

    string dataDir = AppDomain.CurrentDomain.GetData(s_strDataDir) as string;
    if (string.IsNullOrEmpty(dataDir)) {
        string appPath = null;

#if !FEATURE_PAL // FEATURE_PAL does not support ProcessModule
        Process p = Process.GetCurrentProcess();
        ProcessModule pm = (p != null ? p.MainModule : null);
        string exeName = (pm != null ? pm.FileName : null);

        if (!string.IsNullOrEmpty(exeName))
            appPath = Path.GetDirectoryName(exeName);
#endif // !FEATURE_PAL

        if (string.IsNullOrEmpty(appPath))
            appPath = Environment.CurrentDirectory;

        dataDir = Path.Combine(appPath, HttpRuntime.DataDirectoryName);
        AppDomain.CurrentDomain.SetData(s_strDataDir, dataDir, new FileIOPermission(FileIOPermissionAccess.PathDiscovery, dataDir));
    }

    return dataDir;
}

How to find the mysql data directory from command line in windows

You can issue the following query from the command line:

mysql -uUSER -p -e 'SHOW VARIABLES WHERE Variable_Name LIKE "%dir"'

Output (on Linux):

+---------------------------+----------------------------+
| Variable_name             | Value                      |
+---------------------------+----------------------------+
| basedir                   | /usr                       |
| character_sets_dir        | /usr/share/mysql/charsets/ |
| datadir                   | /var/lib/mysql/            |
| innodb_data_home_dir      |                            |
| innodb_log_group_home_dir | ./                         |
| lc_messages_dir           | /usr/share/mysql/          |
| plugin_dir                | /usr/lib/mysql/plugin/     |
| slave_load_tmpdir         | /tmp                       |
| tmpdir                    | /tmp                       |
+---------------------------+----------------------------+

Output (on macOS Sierra):

+---------------------------+-----------------------------------------------------------+
| Variable_name             | Value                                                     |
+---------------------------+-----------------------------------------------------------+
| basedir                   | /usr/local/mysql-5.7.17-macos10.12-x86_64/                |
| character_sets_dir        | /usr/local/mysql-5.7.17-macos10.12-x86_64/share/charsets/ |
| datadir                   | /usr/local/mysql/data/                                    |
| innodb_data_home_dir      |                                                           |
| innodb_log_group_home_dir | ./                                                        |
| innodb_tmpdir             |                                                           |
| lc_messages_dir           | /usr/local/mysql-5.7.17-macos10.12-x86_64/share/          |
| plugin_dir                | /usr/local/mysql/lib/plugin/                              |
| slave_load_tmpdir         | /var/folders/zz/zyxvpxvq6csfxvn_n000009800002_/T/         |
| tmpdir                    | /var/folders/zz/zyxvpxvq6csfxvn_n000009800002_/T/         |
+---------------------------+-----------------------------------------------------------+

Or if you want only the data dir use:

mysql -uUSER -p -e 'SHOW VARIABLES WHERE Variable_Name = "datadir"'

These commands work on Windows too, but you need to invert the single and double quotes.

Btw, when executing which mysql in Linux as you told, you'll not get the installation directory on Linux. You'll only get the binary path, which is /usr/bin on Linux, but you see the mysql installation is using multiple folders to store files.

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If you need the value of datadir as output, and only that, without column headers etc, but you don't have a GNU environment (awk|grep|sed ...) then use the following command line:

mysql -s -N -uUSER -p information_schema -e 'SELECT Variable_Value FROM GLOBAL_VARIABLES WHERE Variable_Name = "datadir"'

The command will select the value only from mysql's internal information_schema database and disables the tabular output and column headers.

Output on Linux:

/var/lib/mysql

Getting the sql server default backup folder on Linux with T-SQL

I've never found a non-registry way to get the backup directory reliably in t-sql. I usually just do a replace of /data/ to /backup/ since at default install it's relation to the data directory is clear. This does not directly answer your question but it's a working way provided you have not done individual directory customization during install.

-- for one of my databases, [dharma] in my linux test-bed.
declare @bkup nvarchar(1024)
set @bkup = replace(cast(SERVERPROPERTY('instancedefaultdatapath') as nvarchar(512)),'/data/','/backup/') + 'dharma.bak'
backup database dharma to disk = @bkup

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