Focusing SQL Queries

More Batmobile purchases Let's explore alternative ways to list our buyers of Batmobiles. In my view, as a general rule, distinct at the top level should be avoided whenever possible. The reason is that if we have overlooked a join condition, a distinct will hide the problem. Admittedly this is a greater risk when building queries with the older syntax, but nevertheless still a risk when using the ANSI/SQL92 syntax if tables are joined through several columns. It is usually much easier to spot duplicate rows than it is to identify incorrect data. It's easy to give a proof of the assertion ...