mongo数组修改器—$push、$ne、$addtoset、$pop、$pull

这几个方法也很有意思

$push

像已有的数组末尾加入一个元素，要是元素不存在，就会创建一个新的元素，如果元素存在了，就会再添加一个一模一样的元素，会造成元素的重复，所以在使用的时候，要确保该元素不存在

元数据

{
    "_id" : ObjectId("5be8e73cba5ba9887ff2f8c4"),
    "Level" : "本科",
    "ProfessionalName" : "数学类",
    "Scope" : [
        "物理"
    ],
    "ContainsProfessional" : [
        "数学与应用数学",
        "统计学",
        "数学与应用数学(拔尖实验班)"
    ],
    "ScopeStatus" : 1,
    "SchoolMid" : "5b3e0926c26dec21807ec5c5"
}

db.getCollection('TestData').update({"_id" : ObjectId("5be8e73cba5ba9887ff2f8c4")},{"$push":{"Scope":"物理"}})

结果

{
    "_id" : ObjectId("5be8e73cba5ba9887ff2f8c4"),
    "Level" : "本科",
    "ProfessionalName" : "数学类",
    "Scope" : [
        "物理",
        "物理"
    ],
    "ContainsProfessional" : [
        "数学与应用数学",
        "统计学",
        "数学与应用数学(拔尖实验班)"
    ],
    "ScopeStatus" : 1,
    "SchoolMid" : "5b3e0926c26dec21807ec5c5"
}

如果想要用$push实现不重复更新，可以和$ne结合使用，

$ne 不在

物理不在Scope数组里，才更新

db.getCollection('TestData').update({"_id" : ObjectId("5be8e73cba5ba9887ff2f8c4"),"Scope":{"$ne":"物理"}},{"$push":{"Scope":"物理"}})

$addtoset

往数组里面加入数据，如果数组里已经存在，则不会加入（避免重复）

addToSet"和"addToSet"和"each”组合起来，可以添加多个不同的值

db.getCollection('TestData').update({"_id" : ObjectId("5be8e73cba5ba9887ff2f8c4")},{"$addToSet":{"Scope":{"$each":["物理","化学"]}}})

返回：Updated 1 existing record(s) in 1ms 一毫秒更新了

**将”addToSet"和"addToSet"和"each”组合起来，可以添加多个不同的值，二用”ne"和"ne"和"push”组合就不能实现**

# 原数据
{
    "_id" : ObjectId("5be8e73cba5ba9887ff2f8c4"),
    "Level" : "本科",
    "ProfessionalName" : "数学类",
    "Scope" : [
        "物理"
    ],
    "ContainsProfessional" : [
        "数学与应用数学",
        "统计学",
        "数学与应用数学(拔尖实验班)"
    ],
    "ScopeStatus" : 1,
    "SchoolMid" : "5b3e0926c26dec21807ec5c5"
}

# 修改后
{
    "_id" : ObjectId("5be8e73cba5ba9887ff2f8c4"),
    "Level" : "本科",
    "ProfessionalName" : "数学类",
    "Scope" : [
        "物理",
        "化学"
    ],
    "ContainsProfessional" : [
        "数学与应用数学",
        "统计学",
        "数学与应用数学(拔尖实验班)"
    ],
    "ScopeStatus" : 1,
    "SchoolMid" : "5b3e0926c26dec21807ec5c5"
}

$pop

删除数组元素，只能从头部或尾部删除一个元素

{
    "_id" : ObjectId("5be8e73cba5ba9887ff2f8c4"),
    "Level" : "本科",
    "ProfessionalName" : "数学类",
    "Scope" : [
        "物理",
        "化学"
    ],
    "ContainsProfessional" : [
        "数学与应用数学",
        "统计学",
        "数学与应用数学(拔尖实验班)"
    ],
    "ScopeStatus" : 1,
    "SchoolMid" : "5b3e0926c26dec21807ec5c5"
}

从Scope数组中末尾开始删除

db.getCollection('TestData').update({"_id" : ObjectId("5be8e73cba5ba9887ff2f8c4")},{"$pop":{"Scope":1}})

{
    "_id" : ObjectId("5be8e73cba5ba9887ff2f8c4"),
    "Level" : "本科",
    "ProfessionalName" : "数学类",
    "Scope" : [
        "物理"
    ],
    "ContainsProfessional" : [
        "数学与应用数学",
        "统计学",
        "数学与应用数学(拔尖实验班)"
    ],
    "ScopeStatus" : 1,
    "SchoolMid" : "5b3e0926c26dec21807ec5c5"
}

从Scope数组中头部开始删除

db.getCollection('TestData').update({"_id" : ObjectId("5be8e73cba5ba9887ff2f8c4")},{"$pop":{"Scope":-1}})

$pull

删除数组元素，将所有匹配的元素删除。

{
    "_id" : ObjectId("5be8e73cba5ba9887ff2f8c4"),
    "Level" : "本科",
    "ProfessionalName" : "数学类",
    "Scope" : [
        "物理",
        "物理",
        "化学"
    ],
    "ContainsProfessional" : [
        "数学与应用数学",
        "统计学",
        "数学与应用数学(拔尖实验班)"
    ],
    "ScopeStatus" : 1,
    "SchoolMid" : "5b3e0926c26dec21807ec5c5"
}

想要删除物理

db.getCollection('TestData').update({"_id" : ObjectId("5be8e73cba5ba9887ff2f8c4")},{"$pull":{"Scope":"物理"}})

{
    "_id" : ObjectId("5be8e73cba5ba9887ff2f8c4"),
    "Level" : "本科",
    "ProfessionalName" : "数学类",
    "Scope" : [
        "化学"
    ],
    "ContainsProfessional" : [
        "数学与应用数学",
        "统计学",
        "数学与应用数学(拔尖实验班)"
    ],
    "ScopeStatus" : 1,
    "SchoolMid" : "5b3e0926c26dec21807ec5c5"
}

注意：会把符合条件的所有元素都删掉

管道中$push和$addToSet

$push	在结果文档中插入值到一个数组中。	db.mycol.aggregate([{$group : {_id : "$by_user", url : {$push: "$url"}}}])
$addToSet	在结果文档中插入值到一个数组中，但不创建副本。	db.mycol.aggregate([{$group : {_id : "$by_user", url : {$addToSet : "$url"}}}])

举例：

三条数据

{
    "_id" : ObjectId("5be8e73cba5ba9887ff2f8c4"),
    "Level" : "本科",
    "ProfessionalName" : "数学类",
    "Scope" : [
        "化学"
    ],
    "ContainsProfessional" : [
        "数学与应用数学",
        "统计学",
        "数学与应用数学(拔尖实验班)"
    ],
    "ScopeStatus" : 1,
    "SchoolMid" : "5b3e0926c26dec21807ec5c5"
}

/* 2 */
{
    "_id" : ObjectId("5be8e7a9ba5ba9887ff2f8d5"),
    "Level" : "本科",
    "ProfessionalName" : "社会科学试验班",
    "Scope" : [],
    "ContainsProfessional" : [
        "社会学",
        "经济学(实验班)",
        "国际经济与贸易(瀚德实验班)",
        "金融学",
        "会计学",
        "人力资源管理",
        "公共事业管理",
        "法学(瀚德实验班)",
        "法学(卓越实验班)",
        "工商管理(商务实验班)"
    ],
    "ScopeStatus" : 0,
    "SchoolMid" : "5b3e0926c26dec21807ec5c5"
}

/* 3 */
{
    "_id" : ObjectId("5be8e85dba5ba9887ff2f8ec"),
    "Level" : "本科",
    "ProfessionalName" : "物理学类",
    "Scope" : [
        "物理"
    ],
    "ContainsProfessional" : [
        "天文学",
        "计算机科学与技术",
        "电子信息科学与技术",
        "管理科学",
        "信息管理与信息系统",
        "物理学(协同创新实验班)",
        "物理学(基地班)",
        "物理学(拔尖实验班)"
    ],
    "ScopeStatus" : 1,
    "SchoolMid" : "5b3e0926c26dec21807ec5c5"
}

$push

在结果文档中插入值到一个数组中

db.getCollection('TestData').aggregate([{"$match" :{"Level":"本科"}}, {"$project":{"Level":1, "ProfessionalName":1, "Scope":1}}, {"$group":{ "_id":"$Level", "schedule":{"$push":{"leave":"$Level","professionalName":"$ProfessionalName","scope":"$Scope"}}}}])

结果

{
    "_id" : "本科",
    "schedule" : [
        {
            "leave" : "本科",
            "professionalName" : "数学类",
            "scope" : [
                "化学"
            ]
        },
        {
            "leave" : "本科",
            "professionalName" : "社会科学试验班",
            "scope" : []
        },
        {
            "leave" : "本科",
            "professionalName" : "物理学类",
            "scope" : [
                "物理"
            ]
        }
    ]
}

$addToSet

在结果文档中插入值到一个数组中，但不创建副本。

db.getCollection('TestData').aggregate([{"$match" :{"Level":"本科"}}, {"$project":{"Level":1, "ProfessionalName":1, "Scope":1}}, {"$group":{ "_id":"$Level", "schedule":{"$addToSet":{"leave":"$Level","professionalName":"$ProfessionalName","scope":"$Scope"}}}}])

结果

{
    "_id" : "本科",
    "schedule" : [
        {
            "leave" : "本科",
            "professionalName" : "物理学类",
            "scope" : [
                "物理"
            ]
        },
        {
            "leave" : "本科",
            "professionalName" : "社会科学试验班",
            "scope" : []
        },
        {
            "leave" : "本科",
            "professionalName" : "数学类",
            "scope" : [
                "化学"
            ]
        }
    ]
}

肉眼观察似乎除了展示顺序有变化，其他貌似没有变化

相关文档

https://www.cnblogs.com/zzy-9318/p/10022651.html