僅對現有字段排序

我有這樣的集合。只有少數用戶有sortOrder場僅對現有字段排序

[{ 
    "_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, 
}]

當我排序sort({"sortOrder": 1})我得到這個

[{ 
    "_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, 
}]

但我需要這樣的排序集合（值與前場sortOrder）

[ { 
    "_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 ", 
}]

我該寫些什麼查詢才能得到它？

來源

2017-10-10 Тарас Мацюк

它看起來並不像你確切使用情況下是支持的，但也有一些解決方法/其他方法可能會讓你得到你想要的。請參閱https://stackoverflow.com/questions/36028267/mongodb-sort-by-only-exists-entry-key-with-value-first-and-key-with-null-or-not和https：// stackoverflow .COM /問題/ 32680809/MongoDB的排序逐場存在的，和當時的字母 –

db.collection.aggregate {$ project：{「_id」：1，「sortOrder」：1，「name」：1，「sortOrder」：{「$ ifNull」：[「$ sortOrder」「」]}}}，{ $排序：{中將sortOrder：1}}

]）

來源

2017-10-10 14:04:14

您可以使用回調來處理幾乎任何方式的排序。

雖然我的解決辦法是令人作嘔低效（遺憾），它的工作原理：

array.sort(function (a, b) { 
    if (a.sortOrder == undefined && b.sortOrder == undefined) { 
    return 0; 
    } 
    if (a.sortOrder == undefined) { 
    return 1; 
    } 
    if (b.sortOrder == undefined) { 
    return -1; 
    } 
    if (a.sortOrder > b.sortOrder) { 
    return 1; 
    } 
    if (a.sortOrder < b.sortOrder) { 
    return -1; 
    } 

    return 0; 
});

的a和b的變量這裏的陣列中的元件，並且這裏返回-1它移動到所述陣列的所述前，0不會改變，1會將它移回數組，如果這是有道理的。

來源

2017-10-10 13:48:25

僅對現有字段排序

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