To change customtable.oldname to customtable.newname:
First, rename the table using SQL Server Management Studio from “customtable_oldname” to “customtable_newname”.
Then, edit the custom table from Site Manager -> Development -> Custom Tables and change the display name and the second part of the code name to newname.
Next, run the following SQL statement against your Kentico database:
SET [ClassTableName] = 'customtable_newname'
WHERE [ClassTableName] = 'customtable_oldname'
Finally, edit the table from the Site Manager again and switch to the Queries tab. Update all of the queries to refer to the new table name.