mysql - 使用父 ID 从单个表中选择和连接数据

Question

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Answer 1

我最终使用了以下内容:

SELECT
    CASE
        WHEN t2.topic IS NULL then t1.topic
        WHEN t3.topic IS NULL then concat(t2.topic, ' / ', t1.topic)
        ELSE concat(t3.topic, ' / ', t2.topic, ' / ', t1.topic)
    END as help_topic
FROM 
    Support_help_topic AS t1
LEFT JOIN 
    Support_help_topic AS t2 ON t2.topic_id = t1.topic_pid
LEFT JOIN 
    Support_help_topic AS t3 ON t3.topic_id = t2.topic_pid
where 
    t1.topic_id = `supptick`.`topic_id`