About database Error

[deltagsm]

i want to ask about this error

Database error in vBulletin 3.6.7:

Invalid SQL:

				SELECT * FROM user AS user
				LEFT JOIN usergroup AS usergroup ON (user.usergroupid = usergroup.usergroupid)
				WHERE user.username = 'Link's_comunication';

MySQL Error  : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 's_comunication'' at line 3
Error Number : 1064

how ti fix this error,

thanks