Firebird 2.1 Language Reference Update

DML statements
Description: A natural join is an automatic equi-join on all the columns that exist in both relations. If there are
no common column names, a CROSS JOIN is produced.
Syntax:
Example:
Notes:
SELECT ...
FROM NATURAL [] JOIN
...
::= {table | view | cte | (select_stmt)} [[AS] alias]
::= INNER | {LEFT | RIGHT | FULL} [OUTER]
select * from Pupils natural left join Tutors
Assuming that the Pupils and Tutors tables have two field names in common: TUTOR and CLASS,
the equivalent traditional syntax is:
select * from Pupils p left join Tutors t
on p.tutor = t.tutor and p.class = t.class
• Common columns can be selected from a natural join without qualifier. Beware, however, that doing so in
outer joins doesn't always gives the same result as selecting left.colname or right.colname. One of the
latter may be NULL while the other isn't; plain colname always returns the non-NULL alternative in such cases.
• SELECT * from a natural join returns each common column only once. In outer joins, such a column always
contains the non-NULL alternative except for rows where the field is NULL in both tables.
ORDER BY
Syntax:
SELECT ... FROM ...
...
ORDER BY [, ...]
::= {col-name | col-alias | col-position | expression}
[COLLATE collation-name]
[ASC[ENDING] | DESC[ENDING]]
[NULLS {FIRST|LAST}]
Order by colum alias
Added in: 2.0
Description: Firebird 2.0 and above support ordering by column alias.
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