带子查询的redshift sql查询中的语法错误

Posted 2021-04-28

我通常在SQL中是一个相当新的人，以前从未处理过redshift。我正在尝试进行一个查询，该查询在postgresql中非常有效。但是我在redshift中遇到语法错误。查询是：

SELECT 
    test.table_1.user_id as user_id,
    test.table_1.timestamp as start_session,
    test.table_1.step_3 :: timestamp +  interval '1 hour' as end_session,
    test.table_1.step_3 :: timestamp +  interval '1 hour' - test.table_1.timestamp :: timestamp as session_duration

FROM (SELECT *,
    min(case when page = 'second_page' then timestamp end) OVER (partition by user_id order by timestamp desc rows between unbounded preceding and unbounded following) as step_2,
    min(case when page = 'third_page' then timestamp end) OVER (partition by user_id order by timestamp desc rows between unbounded preceding and unbounded following) as step_3
    FROM test.table_1) test.table_1

WHERE 
    test.table_1.page = 'first_page' AND
    step_2 > test.table_1.timestamp AND
    step_3 > step_2 AND
    step_3 :: timestamp - step_2 :: timestamp < '1 hour' AND
    step_2 :: timestamp - test.table_1.timestamp :: timestamp < '1 hour'
ORDER BY
    user_id,start_session

Error running query: syntax error at or near "." LINE 11: FROM test.vimbox_pages) test.vimbox_pages ^行中的错误是FROM test.table_1) test.table_1我不明白那里出了什么问题。通过此查询，我试图以某种顺序获取页面阅读过程中用户操作的会话列表。感谢您的帮助！

答案

别名是标识符，需要遵循标识符规则。您还可以通过其他方式简化查询：

SELECT t.user_id, t.timestamp as start_session,
       (t.step_3::timestamp + interval '1 hour' as end_session),
       (t.step_3::timestamp + interval '1 hour' - t.timestamp::timestamp) as session_duration
FROM (SELECT t.*,
             MIN(CASE WHEN page = 'second_page' THEN timestamp END) OVER (PARTITION BY user_id) as step_2,
             MIN(CASE WHEN page = 'third_page' THEN timestamp END) OVER (partition by user_id) as step_3
      FROM test.table_1 t
     ) t
WHERE t.page = 'first_page' AND
      step_2 > t.timestamp AND
      step_3 > step_2 AND
      step_3::timestamp < step_2::timestamp + interval '1 hour' AND
      step_2::timestamp < timestamp + interval '1 hour'
ORDER BY user_id, start_session;

注意：

• 您的窗口条款不必要地复杂。如果要整个窗口范围，则不需要ORDER BY。
• 给定列名，到timestamp的转换应该是不必要的。但是我留给他们了。
• t.user_id as user_id是多余的。列名将始终为user_id。
• 我从没看到::周围的空格。当然可以允许它们，但是类型转换的优先级很高，并且通常不带空格。
• 我更喜欢时间戳比较而不是时间戳，而不是转换为间隔。奇怪的事情有时会发生。