Firebird 2.1 Language Reference Update

DML statements
select d.dept_no,
d.indent || d.department as department,
dyb_2008.budget as budget_08,
dyb_2009.budget as budget_09
from dept_tree d
left join dept_year_budget dyb_2008
on d.dept_no = dyb_2008.dept_no
and dyb_2008.fiscal_year = 2008
left join dept_year_budget dyb_2009
on d.dept_no = dyb_2009.dept_no
and dyb_2009.fiscal_year = 2009
Notes on recursive CTEs:
• Aggregates (DISTINCT, GROUP BY, HAVING) and aggregate functions (SUM, COUNT, MAX etc) are not
allowed in recursive union members.
• A recursive reference cannot participate in an outer join.
• The maximum recursion depth is 1024.
Derived tables (“SELECT FROM SELECT”)
Added in: 2.0
Description: A derived table is the result set of a SELECT query, used in an outer SELECT as if it were an ordinary
table. Put otherwise, it is a subquery in the FROM clause.
Syntax:
Examples:
(select-query)
[[AS] derived-table-alias]
[()]
:= column-alias [, column-alias ...]
The derived table in the query below (shown in boldface) contains all the relation names in the
database followed by their field count. The outer SELECT produces, for each existing field count, the
number of relations having that field count.
select fieldcount,
count(relation) as num_tables
from (select r.rdb$relation_name as relation,
count(*) as fieldcount
from rdb$relations r
join rdb$relation_fields rf
on rf.rdb$relation_name = r.rdb$relation_name
group by relation)
group by fieldcount
A trivial example demonstrating the use of a derived table alias and column aliases list (both are
optional):
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