PostgreSQL:我需要在 CTE 中返回任何内容吗？

Question

我曾经听说 CTE(WITH 语句)需要返回一些东西。否则可能会发生不执行的情况。

我有以下 CTE 简化结构:

WITH
selectA AS (
    SELECT ...
),
insertA AS (
    INSERT INTO ...
    -- selecting something from selectA
    RETURNING ...
),
insertB AS (
    INSERT INTO ... 
    -- selecting something from selectA and insertA
    -- HERE no RETURNING!
),
selectB AS (
    SELECT ...
    -- selecting something from selectA and insertA
),
insertForms AS (
    INSERT INTO ...
    -- selecting something from selectB
    -- HERE no RETURNING!
),
insertFormData AS (
    INSERT INTO ...
    -- selecting something from selectB
    -- HERE no RETURNING!
)
SELECT ...
    -- selecting something from insertA and selectB

它有效，但我想知道我是否遇到了导致所有 CTE 部分都被执行的极端情况。 在 PostgreSQL 文档中，我没有找到 CTE 中是否需要返回部分的明确提示。

有人对此有好的想法吗？ 非常感谢!

Answer 1

“但我想知道我是否遇到了任何极端情况”- 该行为已被完整记录 in the manual

If RETURNING is omitted, the statement is still executed, but it produces no output so it cannot be referenced as a table by the primary query