Your query would've displayed any data that was available. If there is no data in the TC_HOST_NAME column, then you have not entered any data for that field into the database.
TESTCYCL is the data displayed in the Execution Grid for a Test Set in the Test Lab module. If you don't see Planned Host Name data there (assuming you have that column displayed in the UI) then there is nothing for the SQL query to show you.
(Opinions and information contained in this post are wholly my own and do not reflect the opinions of my employer.)