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Walden H. Leverich wrote:
CRPence wrote:
IMO the most obvious reason, is to enable ISAM versus SQL access
to the data via...

OK, but then create an LF over the table. Why take a SQL concept
(view) and try to use it in HLL-IO? If you want a LF create an LF,
complete w/the necessary DDS. I don't believe there's a restriction
to creating an LF over a PF that is a SQL table, is there?

A DDS LF, simply put, does not support the many desirable features and mappings that are available via an SQL SELECT. A DDS LF does not support any of, for example, HEX(), character to numeric, CASE, GROUP BY, AVG, date arithmetic, scalar UDF, et al.

FWiW, given my choice, an ORDER BY in a VIEW would have more intuitively satisfied the concept; i.e. rather than an INDEX that is over a VIEW. Regardless, my points are both that ordering the result of a VIEW may be desirable for ISAM and that OPNQRYF of a VIEW may be able to effect that in many cases, to accomplish what is desired.

The better question I think is: Why *not* take advantage of the SQL concept (VIEW) and use it to remove logic from the HLL, when it can be replaced easily by what the database already provides? Since CLP is very limited in its file I/O, it can obviously benefit significantly more from being able to push the logic down to the database than a language like RPG. However at the same time, there is no reason RPG should not be able to benefit similarly.

Oddly, I seem to have failed to paste additional text I had composed separately, that mentioned that DB2 for i [with IBM i 6.1] offers some new function for CREATE INDEX. I will make a separate reply to the OP. That new function enables an SQL INDEX to be created with some mapping [expressions; e.g. HEX(), etc.] and selection [WHERE clause], very similar to the DDS LF derived [keyed] [select/omit] indexes. Note: the capability of the optimizer to use these indexes [until the next release] may actually be more limited than for what capabilities can be achieved using them with RLA. Refer to the revised SQL syntax:
http://publib.boulder.ibm.com/infocenter/systems/topic/db2/rbafzxcindx.htm

Regards, Chuck

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