Issue with recursive CTE in PostgreSQL

问题

This query generates the numbers from 1 to 4.

with recursive z(q) as (
  select 1
  union all
  select q + 1 from z where q < 4
  )
select * from z;

But, if I modify it to this,

with x as (
  select 1 y
  ),
recursive z(q) as (
  select y from x
  union all
  select q + 1 from z where q < 4
  )
select * from z;

It gives

ERROR: syntax error at or near "z"

What did i do wrong here?

回答1:

I think this is because RECURSIVE is modifier of WITH statement, not a property of common table expression z, so you can use it like this:

with recursive
x as (
  select 1 y
),
z(q) as (
  select y from x
  union all
  select q + 1 from z where q < 4
)
select * from z;

sql fiddle demo

来源：https://stackoverflow.com/questions/19420168/issue-with-recursive-cte-in-postgresql