Re: SQL 'Select AS' syntax

[CRPence <crp@xxxxxxxxxxxxxxxxxxxx>]

  With INNER JOIN the WHERE for join selection should always be the 
same.  Thus why the QMQRY output was and remains valid, from its 
availability prior to the JOIN syntax.

  I think some other responses were over-presumptive on what should be 
expected when using WHERE clause to do joins, beyond the INNER JOIN. 
Albeit I do not recall any more than the simples case of only the join 
selection being specified.  However...

  For any other JOIN type [than INNER JOIN] it is probably best to be 
in the habit of explicitly stating the JOIN ON, because the intent to 
the query engine may become ambiguous when there are any more selections 
than the between-file tests to effect the join.  In such an ambiguous 
request, the query engine is not obligated to operate in the way you 
have assumed it will.  The outcome could include a possibly changing 
result set.  For example in an OUTER JOIN, some WHERE clause selections 
could limit the results prior to the join selection; e.g. because the 
optimizer found an index that quickly limits the rows to be joined, and 
because no join selection rules were explicitly stated there is no 
requirement to order when the selection occurs.

  So rather than as a "performance boost", make a habit of avoiding use 
of the WHERE clause for join to prevent surprises; be explicit in your 
intentions for the SQL request that is sent to the query engine.

Regards, Chuck