Question

我有这样的集合。只有少数用户拥有sortOrder字段

[{
    "_id": "59ccf78bde3d14019169c105",
    "name": "Best FX broker ",
},
{
    "_id": "59ccf78bde3d14019169c102",
    "name": "Best automated Performance tool ",
    "sortOrder": 1,
},
{
    "_id": "59ccf78bde3d14019169c104",
    "name": "Best Regtech/ reporting solution ",
},
{
    "_id": "59ccf78bde3d14019169c106",
    "name": "NEW: BEST CRYPTO SERVICE PROVIDER",
    "sortOrder": 2,
}]

当我按sort({"sortOrder": 1})排序时，我得到了这个

[{
    "_id": "59ccf78bde3d14019169c105",
    "name": "Best FX broker ",
},
{
    "_id": "59ccf78bde3d14019169c104",
    "name": "Best Regtech/ reporting solution ",
},
{
   "_id": "59ccf78bde3d14019169c102",
    "name": "Best automated Performance tool ",
    "sortOrder": 1,
},
{
    "_id": "59ccf78bde3d14019169c106",
    "name": "NEW: BEST CRYPTO SERVICE PROVIDER",
    "sortOrder": 2,
}]

但是我需要像这样排序集合（顶部有sortOrder的值）

[ {
   "_id": "59ccf78bde3d14019169c102",
    "name": "Best automated Performance tool ",
    "sortOrder": 1,
},
{
    "_id": "59ccf78bde3d14019169c106",
    "name": "NEW: BEST CRYPTO SERVICE PROVIDER",
    "sortOrder": 2,
},
{
    "_id": "59ccf78bde3d14019169c105",
    "name": "Best FX broker ",
},
{
    "_id": "59ccf78bde3d14019169c104",
    "name": "Best Regtech/ reporting solution ",
}]

我应该写什么查询才能得到这个？

Answer 1

db.collection.aggregate（[ {$ project：{“_ id”：1，“sortOrder”：1，“name”：1，“sortOrder”：{“$ ifNull”：[“$ sortOrder”，“”]}}}， {$ sort：{sortOrder：1}}

]）

Answer 2

您可以使用回调几乎以任何方式处理排序。

虽然我的解决方案令人作呕的效率很低（抱歉），但它确实有效：

null

这里的a和b变量是数组中的元素，这里返回-1将它移动到数组的前面，0不会改变，1将它移回数组，如果这是有道理的。

仅排序现有字段

2 个答案: