Firebird 2.1 Language Reference Update

Syntax:
Example:
Notes:
::=
DML statements
::= WITH [RECURSIVE] [, ...]
::= name [()] AS ()
::= column-alias [, column-alias ...]
::= any SELECT statement or UNION
::= the main SELECT statement, which can refer to the
CTEs defined in the preamble
with dept_year_budget as (
select fiscal_year,
dept_no,
sum(projected_budget) as budget
from proj_dept_budget
group by fiscal_year, dept_no
)
select d.dept_no,
d.department,
dyb_2008.budget as budget_08,
dyb_2009.budget as budget_09
from department 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
where exists (
select * from proj_dept_budget b
where d.dept_no = b.dept_no
)
• A CTE definition can contain any legal SELECT statement, as long as it doesn't have a “WITH...” preamble
of its own (no nesting).
• CTEs defined for the same main query can reference each other, but care should be taken to avoid loops.
• CTEs can be referenced from anywhere in the main query.
• Each CTE can be referenced multiple times in the main query, possibly with different aliases.
• When enclosed in parentheses, CTE constructs can be used as subqueries in SELECT statements, but also in
UPDATEs, MERGEs etc.
• In PSQL, CTEs are also supported in FOR loop headers:
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