Обсуждение: Is "WITH RECURSIVE" limited to the first position of CTEs by design?

Поиск
Список
Период
Сортировка

Is "WITH RECURSIVE" limited to the first position of CTEs by design?

От
Kirk Wolak
Дата:
Team,
  This was strange.  I wanted to set up a CTE that would FEED my recursive query.
And also feed the results filtering...

These are the most trivial examples.  The second one results in a syntax error.  Which implies that:
1) There can only be one recursive CTE at the same level?
2) It must be the FIRST CTE?

Example:
WITH RECURSIVE CTE1 AS (select 2 UNION ALL SELECT 0),
CTE2 AS (select 1 UNION ALL SELECT 0) select 3 ;

-- This does not work:

WITH CTE1 AS (select 2 UNION ALL SELECT 0),
RECURSIVE CTE2 AS (select 1 UNION ALL SELECT 0)
SELECT 3;
--> ERROR:  syntax error at or near "CTE2"

Thanks in advance...

Kirk

Re: Is "WITH RECURSIVE" limited to the first position of CTEs by design?

От
"David G. Johnston"
Дата:
On Mon, Nov 13, 2023 at 9:17 AM Kirk Wolak <wolakk@gmail.com> wrote:
These are the most trivial examples.  The second one results in a syntax error.  Which implies that:
1) There can only be one recursive CTE at the same level?
2) It must be the FIRST CTE?

There is only one WITH keyword as well, that doesn't change the fact there can be multiple attached queries to it.

The documentation explains clearly the implications on adding the keyword RECURSIVE after the keyword WITH.

https://www.postgresql.org/docs/current/sql-select.html#SQL-WITH

David J.

Re: Is "WITH RECURSIVE" limited to the first position of CTEs by design?

От
Tom Lane
Дата:
"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Mon, Nov 13, 2023 at 9:17 AM Kirk Wolak <wolakk@gmail.com> wrote:
>> These are the most trivial examples.  The second one results in a syntax
>> error.  Which implies that:
>> 1) There can only be one recursive CTE at the same level?
>> 2) It must be the FIRST CTE?

> There is only one WITH keyword as well, that doesn't change the fact there
> can be multiple attached queries to it.

Yeah, RECURSIVE is attached to the WITH not to the query.  That's
because it has global implications for the visibility of the CTE
names across all the CTEs in the WITH.

            regards, tom lane