Same column name from different table

Question

i have a sql query as like this : "SELECT * FROM TABLE1,TABLE2". i use oracle. both TABLE1 and TABLE2 have the same column named 'COLUMN1'. while i get rows how i know the value of COLUMN1 from which table (TABLE1 or TABLE2).
sample code snippet is above. do u help me!
while (rs.next())
value1 = rs.getString("COLUMN1");
// is value1's value from table1 or table2. how do i know this?
// i try value1 = rs.getString("TABLE1.COLUMN1"); but it doesn't work :(
....

Answer 1

I case you don't know what an alias is, it would look something like this:
SELECT a.COLUMN1 as FirstColumn1, b.COLUMN1 as SecondColumn1 FROM FirstTable a, SecondTable b
Notice that in the FROM clause we've appended a short name for each table. You're not limited to one character, but I try to keep it simple. Now we can refer to the tables as a and b.
Because I did that I have to refer to any ambiguous columns (although it's good practice to refer to ALL columns) using the table name prefix and a period. This tells the driver which "COLUMN1" I want. Then we include as AS clause which allows us to tell the driver what we want that column name to be when it's returned to us. This is specially usefule when I have two columns in two separate tables with the same name (as you have here) or if I'm calculating data (i.e. (a.QTY * b.PRICE) as UnitPrice) that doesn't have a column name, so here I can give it one.
It's a little weird at first since you use the alias names in the select before you actually define them in the FROM clause, but you'll get use to it.
Now you retrieve FirstColumn1 and SecondColumn1 from your ResultSet, not Column1.
HTH.