如何使用 WITH 子查询更新或插入数据？并避免`PG::UndefinedTable: ERROR: missing FROM-clause entry for table`错误答案

【问题标题】：How to update or insert data with WITH subquery? and avoid `PG::UndefinedTable: ERROR: missing FROM-clause entry for table` error如何使用 WITH 子查询更新或插入数据？并避免`PG::UndefinedTable: ERROR: missing FROM-clause entry for table`错误
【发布时间】：2020-09-27 08:31:18
【问题描述】：

我正在尝试运行简单的 sql 查询：

    <<-SQL.squish
      WITH payloads as (
        INSERT into text_payloads (text, created_at, updated_at)
          SELECT text, created_at, updated_at
          FROM text_messages
        RETURNING id, text, created_at, updated_at
      )
      UPDATE text_messages
      SET
        payload_id = text_payloads.id,
        payload_type = 'TextPayload'
      WHERE
        text_messages.text = text_payloads.text AND
        text_messages.created_at = text_payloads.created_at AND
        text_messages.updated_at = text_payloads.updated_at
    SQL

但出现此错误：

PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "text_payloads"
LINE 1: ...d_type = 'TextPayload' WHERE text_messages.text = text_paylo...

我已经尝试添加FROM payloads 甚至LEFT OUTER JOIN text_payloads，但没有任何帮助。如何使用WITH 子查询及其结果实现此更新或类似的插入操作？

非常感谢您！

【问题讨论】：

标签： sql postgresql pg

【解决方案1】：

错误信息很明确：UPDATE 语句中没有 FROM 子句来执行 CTE 之间的连接（我猜你想使用 CTE 而不是 text_payloads) 和 text_messages.
正确的语法是：

WITH payloads as (
  INSERT into text_payloads (text, created_at, updated_at)
    SELECT text, created_at, updated_at
    FROM text_messages
  RETURNING id, text, created_at, updated_at
)
UPDATE text_messages
SET
  payload_id = payloads.id,
  payload_type = 'TextPayload'
FROM payloads  
WHERE
  text_messages.text = payloads.text AND
  text_messages.created_at = payloads.created_at AND
  text_messages.updated_at = payloads.updated_at

请参阅demo。

【讨论】：

【解决方案2】：

这是工作代码

    <<-SQL.squish
      WITH payloads as (
        INSERT into text_payloads (text, created_at, updated_at)
          SELECT text, created_at, updated_at
          FROM text_messages
        RETURNING id, text, created_at, updated_at
      )
      UPDATE text_messages
      SET
        payload_id = text_payloads.id,
        payload_type = 'TextPayload'
      FROM payloads, text_payloads
      WHERE
        text_messages.text = text_payloads.text AND
        text_messages.created_at = text_payloads.created_at AND
        text_messages.updated_at = text_payloads.updated_at
    SQL

【讨论】：