加入三个表导致重复记录

以下查询几乎是正确的，只是它会导致list_taxonomies表中的重复行。我只需要list_taxonomies表中的唯一行。我一直在努力解决一些解决方案，但似乎无法得到它。我已经试过了项目表上的左外部和内部联接。加入三个表导致重复记录

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查询：

SELECT 
    lists.*, 
    json_agg(items ORDER BY items.id) AS _items, 
    json_agg(list_taxonomies ORDER BY list_taxonomies.type) AS taxonomy 
FROM 
    lists 
JOIN 
    list_taxonomies ON list_taxonomies.list_id = lists.id 
JOIN 
    items ON items.list_id = lists.id 
WHERE 
    lists.id = 3 
GROUP BY 
    lists.id

当前的结果：

{ 
    "status": "success", 
    "data": [{ 
     "id": 3, 
     "name": "tincidunt pede ac urna. Ut", 
     "description": "Lorem ipsum dolor sit amet, consectetuer adipiscing", 
     "created": "2016-08-24T12:00:00.000Z", 
     "updated": "2016-08-24T12:00:00.000Z", 
     "owner": 9, 
     "likes": 3, 
     "private": 0, 
     "location": "United States", 
     "nsfw": 0, 
     "_items": [{ 
      "id": 2, 
      "name": "sem semper", 
      "description": "sollicitudin commodo", 
      "list_id": 3, 
      "type": 2, 
      "image": "http://fillmurray.com/", 
      "list_order": 6, 
      "created": "2016-08-24T05:00:00-07:00", 
      "link": "http://amazon.com" 
     }, { 
      "id": 14, 
      "name": "magna sed", 
      "description": "bibendum. Donec felis", 
      "list_id": 3, 
      "type": 2, 
      "image": "http://fillmurray.com/", 
      "list_order": 1, 
      "created": "2016-08-24T05:00:00-07:00", 
      "link": "http://google.com" 
     }], 
     "taxonomy": [{ 
      "list_id": 3, 
      "taxonomy": "Art", 
      "type": 1 
     }, { 
      "list_id": 3, 
      "taxonomy": "Art", 
      "type": 1 
     }, { 
      "list_id": 3, 
      "taxonomy": "Art", 
      "type": 1 
     }, { 
      "list_id": 3, 
      "taxonomy": "Art", 
      "type": 1 
     }, { 
      "list_id": 3, 
      "taxonomy": "Art", 
      "type": 1 
     }, { 
      "list_id": 3, 
      "taxonomy": "Art", 
      "type": 1 
     }, { 
      "list_id": 3, 
      "taxonomy": "Art", 
      "type": 1 
     }] 
    }], 
    "message": "Retrieved list 1" 
}

来源

2017-02-09 jboneca

与LEFT JOIN尝试 – McNets

@McNets我已经尝试过，结果一样。 – jboneca

应该是分类内部项目？因为双左连接应该起作用。 – McNets

当从多个表汇总，然后汇总加盟之前：

SELECT 
    l.*, 
    i._items, 
    lt.taxonomy 
FROM lists l 
JOIN 
(
    select list_id, json_agg(list_taxonomies.* order by type) AS taxonomy 
    from list_taxonomies 
    group by list_id 
) lt ON lt.list_id = l.id 
JOIN 
(
    select list_id, json_agg(items.* order by id) AS _items 
    from items 
    group by list_id 
) i ON i.list_id = l.id 
WHERE l.id = 3;

来源

2017-02-09 22:44:33

这种情况对我很有意义，但查询失败，因为_items实际上并不是项目中的一列。 – jboneca

不，不是。这是我们的json聚合项目的别名。我在这里没有看到缺陷。也许它需要'item'或者'items。*'而不是'json_agg（* order by id）''中的'*'？什么是你正在得到确切的错误信息？ –

我得到'_items'不存在。你说的没错，*本身就是导致错误的原因。一旦我改变了，那是对的。谢谢！ – jboneca

加入三个表导致重复记录

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