> It seems like I've had a problem once or twice in the past when I didn't > qualify the COL's in something like this, especially with regard to a common > column.
If the following two conditions are true then R:Base will produce correct results: 1. The unqualified column exists only in one table. 2. The unqualified column will have the same value in both tables (because it is used in the JOIN conditions in the form ColName = ColName). The only time you NEED to qualify the column is if it exists in both tables in the JOIN, but has different values. However, it's certainly clearer and good practice to qualify all column names in a multi-table select. Some other SQL dialects require you to do so, even when no ambiguity exists. -- Larry
