Constants, program variables etc. should be on the right hand side of a WHERE or HAVING clause.
Columns requiring to be outer joined should appear on the right hand side of a WHERE or HAVING clause.
Table aliases should be used in all queries that have more than one table in the FROM clause.
The use of table aliases speeds up the parse phase of an oracle query, by reducing the number ofrecursive sql queries.
Notice the table aliases o,l,n and their subsequent use in the where clause.
Ordering of where clauses.
As an aid to understanding, WHERE clauses should be laid out with the join clauses first, and the restriction clauses second.
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