Firebird 2.1 Language Reference Update

Example:
select * from Men cross join Women
order by Men.age, Women.age
DML statements
-- old syntax:
-- select * from Men join Women on 1 = 1
-- order by Men.age, Women.age
-- comma syntax:
-- select * from Men, Women
-- order by Men.age, Women.age
Named colums JOIN
Added in: 2.1
Description: A named colums join is an equi-join on the columns named in the USING clause. These columns
must exist in both relations.
Syntax:
Example:
Notes:
SELECT ...
FROM [] JOIN
USING (colname [, colname ...])
...
::= {table | view | cte | (select_stmt)} [[AS] alias]
::= INNER | {LEFT | RIGHT | FULL} [OUTER]
select *
from books join shelves
using (shelf, bookcase)
The equivalent in traditional syntax:
select *
from books b join shelves s
on b.shelf = s.shelf and b.bookcase = s.bookcase
• The columns in the USING clause can be selected without qualifier. Be aware, however, that doing so in outer
joins doesn't always give 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 named columns join returns each USING 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.
Natural JOIN
Added in: 2.1
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