I have two large tables (~1GB each) with many different columns on which I want to perform a union all in sas.

Currently, I use the following method with proc sql and union all.

`SELECT A, B, '' as C from Table_1 
UNION ALL
SELECT '' as A, B, C from Table_2`

However, this is not preferable as I have dozens of rows in both tables and I am constantly adding to them. Therefore, I am looking for a way to automatically create the blank columns without having to explicitly write them out.

I also tried the following query:  

`select * from
(select * from Table_1), 
(select * from Table_2)`

However, this seems very computationally intensive and takes forever to run.

Are there any better ways to do this? I am also open to using `data set` instead of proc sql;