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  2. JAVA400-L
  3. September 2007

RE: Question using jdbc/jt400

The ONLY time you would not use a pre-defined VIEW or INDEX is when it
is a
truly ad hoc query, which would correspond to the OPNQRYF statement
above.

What about when you're selecting on one set of fields and ordering on
another. Let's say you wanted to display two views of order-details, one
by line-number and on by item-number. In both cases we're talking about
lines for a single order, and our average order has 10 lines.

In ISAM world you would need an index by Order, OrderLineNumber and
another by Order, OrderLineItem, where in SQL you would just need the
index by Order and then let it sort. You're sorting few enough rows that
the sort makes sense. Not to mention, how do you do a view sorted by
item-description? An array?

Point is, in ISAM-land you _must_ have an index, in SQL-land you
_probably should_ have an index, but sometimes you don't need one.

-Walden


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