What is the command to truncate a SQL Server log file?

I need to empty an LDF file before sending to a colleague. How do I force SQL Server to truncate the log?

7 Answers

In management studio:

Don't do this on a live environment, but to ensure you shrink your dev db as much as you can:
- Right-click the database, choose Properties, then Options.
- Make sure "Recovery model" is set to "Simple", not "Full"
- Click OK
Right-click the database again, choose Tasks -> Shrink -> Files
Change file type to "Log"
Click OK.

Alternatively, the SQL to do it:

 ALTER DATABASE mydatabase SET RECOVERY SIMPLE DBCC SHRINKFILE (mydatabase_Log, 1)

Ref:

if I remember well... in query analyzer or equivalent:

BACKUP LOG databasename WITH TRUNCATE_ONLY DBCC SHRINKFILE ( databasename_Log, 1)

For SQL Server 2008, the command is:

ALTER DATABASE ExampleDB SET RECOVERY SIMPLE DBCC SHRINKFILE('ExampleDB_log', 0, TRUNCATEONLY) ALTER DATABASE ExampleDB SET RECOVERY FULL

This reduced my 14GB log file down to 1MB.

For SQL 2008 you can backup log to nul device:

BACKUP LOG [databaseName] TO DISK = 'nul:' WITH STATS = 10

And then use DBCC SHRINKFILE to truncate the log file.

backup log logname with truncate_only followed by a dbcc shrinkfile command

Since the answer for me was buried in the comments. For SQL Server 2012 and beyond, you can use the following:

BACKUP LOG Database TO DISK='NUL:' DBCC SHRINKFILE (Database_Log, 1)

Another option altogether is to detach the database via Management Studio. Then simply delete the log file, or rename it and delete later.

Back in Management Studio attach the database again. In the attach window remove the log file from list of files.

The DB attaches and creates a new empty log file. After you check everything is all right, you can delete the renamed log file.

You probably ought not use this for production databases.