postgresql – 在postgres上使用什么而不是“INSERT … on CONFLICT DO NOTHING”

2023年4月30日 414次阅读

我有以下查询,我使用postgres 9.5：

INSERT INTO knowledge_state 
(SELECT learnerid learner_id, lo_id FROM qb_lo_tag WHERE qb_id = NEW.qb_id)
ON CONFLICT DO NOTHING ;

不幸的是我不能在某些服务器上使用postgres 9.5,我需要将它转换为9.5之前的友好查询.
我已经构建了以下查询,但对我来说似乎要复杂得多,我认为可能更简单.

FOR rows IN SELECT lo_id FROM knowledge_state 
WHERE learner_id = learnerid 
AND lo_id IN (SELECT lo_id FROM qb_lo_tags WHERE qb_id = New.qb_id) LOOP

  INSERT INTO knowledge_state (lo_id, learner_id) SELECT rows.lo_id, learnerid 
WHERE NOT EXISTS (SELECT * FROM knowledge_state WHERE lo_id = rows.lo_id AND learner_id = learnerid);

END LOOP;

我很想听听如何简化此查询的想法.

最佳答案 只是做你正在做的事情,没有循环：

INSERT INTO knowledge_state (lo_id, learner_id) 
SELECT  a.lo_id, a.learnerid
FROM qb_lo_tag a
WHERE a.qb_id = NEW.qb_id
and  NOT EXISTS (SELECT * FROM knowledge_state b 
     WHERE b.lo_id = a.lo_id AND b.learner_id = a.learnerid);

当然,您可以在knowledge_state(lo_id,learner_id)上添加索引以使其更快(On Conflict意味着唯一约束或其他约束,而唯一约束意味着索引).

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