I am trying to insert data from one of my existing table into another existing table.

Is it possible to insert data into any existing table using select * into query. I think it can be done using union but in that case i need to record all data of my existing table into temporary table, then drop that table and finally than apply union to insert all records into same table

eg.

select * into #tblExisting from tblExisting
drop table tblExisting
select * into tblExisting from #tblExisting union tblActualData

Here tblExisting is the table where I actually want to store all data tblActualData is the table from where data is to be appended to tblExisting.

Is it right method. Do we have some other alternative ?