How to get second MAXIMUM DATE in MYSQL

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我在风中等你
我在风中等你 2021-01-29 16:27

I want to fetch my record from mysql db. I want to fetch second maximum date from the record. But i failed

Here is my code

    

        
4条回答
  •  鱼传尺愫
    2021-01-29 17:24

    It wasn't fun to read your query, but I think the problem is here:

    LEFT JOIN (
      SELECT max(notification_date) notification_date, client_id
      FROM og_ratings
      WHERE notification_date NOT IN (
        SELECT max(notification_date)
        FROM og_ratings
    )
    

    if you want the maximum date for every client you need to GROUP BY client_id:

    SELECT client_id, max(notification_date) notification_date
    FROM og_ratings
    GROUP BY client_id
    

    if you want the second maximum there are few options, I'm using this one which is easier to understand but it's not necessarily the most performant:

    SELECT client_id, max(notification_date) notification_date
    FROM og_ratings
    WHERE
      (client_id, notification_date) NOT IN (
        SELECT client_id, max(notification_date)
        FROM og_ratings GROUP BY client_id
      )
    GROUP BY client_id
    

    third problem, you're using a LEFT JOIN which means that you will return all values from og_ratings regardless if they are the second maximum or not. Use INNER JOIN on this context:

    SELECT
      r.client_id,
      c.id,
      t.id,
      ..etc...
    FROM
      og_ratings r INNER JOIN (
        SELECT client_id, max(notification_date) notification_2nd_date
        FROM og_ratings
        WHERE
          (client_id, notification_date) NOT IN (
            SELECT client_id, max(notification_date)
            FROM og_ratings GROUP BY client_id
          )
        GROUP BY client_id
       ) r2
      ON r.notification_date = r2.notification_2nd_date
         AND r.client_id = r2.client_id
      LEFT JOIN og_companies c ON r.client_id = c.id
      LEFT JOIN og_rating_types t ON r.rating_type_id = t.id
      LEFT JOIN og_actions a ON r.pacra_action = a.id
      LEFT JOIN og_outlooks o ON r.pacra_outlook = o.id
      LEFT JOIN og_lterms l ON r.pacra_lterm = l.id
      LEFT JOIN og_sterms s ON r.pacra_sterm = s.id
      LEFT JOIN pacra_client_opinion_relations pr ON pr.opinion_id = c.id
      LEFT JOIN pacra_clients pc ON pc.id = pr.client_id
      LEFT JOIN city ON city.id = pc.head_office_id
    WHERE
      r.client_id IN (
        SELECT opinion_id FROM pacra_client_opinion_relations
        WHERE client_id = 50
      )
    

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