MongoDB之数据查询（数组）

发布时间：2020-08-12 17:45:23 来源：ITPUB博客阅读：129 作者：stonebox1122 栏目：关系型数据库

首先在MongoDB里面是支持数组保存的，一旦支持了数组保存，就需要针对于数组的数据进行匹配。

范例：保存一部分数组内容
db.emp.insert({"name":"刘A","sex":"男","age":35,"sal":8000,"loc":"北京","course":["语文","数学","英语","音乐","政治"]});
db.emp.insert({"name":"刘B","sex":"男","age":35,"sal":8000,"loc":"北京","course":["语文","数学"]});
db.emp.insert({"name":"刘C","sex":"男","age":35,"sal":8000,"loc":"北京","course":["语文","数学","英语"]});
db.emp.insert({"name":"刘D","sex":"男","age":35,"sal":8000,"loc":"北京","course":["语文","数学","政治"]});
db.emp.insert({"name":"刘E","sex":"男","age":35,"sal":8000,"loc":"北京","course":["语文","政治"]});

> db.emp.find().pretty();
{
        "_id" : ObjectId("599108423268c8e84253be26"),
        "name" : "赵一",
        "sex" : "男",
        "age" : 30,
        "sal" : 1000,
        "loc" : "北京"
}
{
        "_id" : ObjectId("599108423268c8e84253be27"),
        "name" : "钱二",
        "sex" : "女",
        "age" : 22,
        "sal" : 5000,
        "loc" : "上海"
}
{
        "_id" : ObjectId("599108423268c8e84253be28"),
        "name" : "孙三",
        "sex" : "男",
        "age" : 40,
        "sal" : 2000,
        "loc" : "深圳"
}
{
        "_id" : ObjectId("599108423268c8e84253be29"),
        "name" : "李四",
        "sex" : "女",
        "age" : 30,
        "sal" : 7000,
        "loc" : "北京"
}
{
        "_id" : ObjectId("599108423268c8e84253be2a"),
        "name" : "周五",
        "sex" : "女",
        "age" : 30,
        "sal" : 6400,
        "loc" : "北京"
}
{
        "_id" : ObjectId("599108423268c8e84253be2b"),
        "name" : "吴六",
        "sex" : "男",
        "age" : 30,
        "sal" : 2500,
        "loc" : "重庆"
}
{
        "_id" : ObjectId("599108423268c8e84253be2c"),
        "name" : "郑七",
        "sex" : "女",
        "age" : 50,
        "sal" : 4700,
        "loc" : "成都"
}
{
        "_id" : ObjectId("599108433268c8e84253be2d"),
        "name" : "王八",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京"
}
{
        "_id" : ObjectId("599129a00184ff511bf02b87"),
        "name" : "刘A",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学",
                "英语",
                "音乐",
                "政治"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b88"),
        "name" : "刘B",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b89"),
        "name" : "刘C",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学",
                "英语"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b8a"),
        "name" : "刘D",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学",
                "政治"
        ]
}
{
        "_id" : ObjectId("599129a20184ff511bf02b8b"),
        "name" : "刘E",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "政治"
        ]
}

此时的数据包含有数组内容，而后需要针对数组数据进行判断，可以使用几个运算符：$all、$size、$slice、$elemMatch

范例：查询同时参加语文和数学课程的人员
现在两个数组内容都需要保存，所以使用“{"$all",[内容1,内容2,...]}”
> db.emp.find({"course":{"$all":["语文","数学"]}}).pretty();
{
        "_id" : ObjectId("599129a00184ff511bf02b87"),
        "name" : "刘A",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学",
                "英语",
                "音乐",
                "政治"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b88"),
        "name" : "刘B",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b89"),
        "name" : "刘C",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学",
                "英语"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b8a"),
        "name" : "刘D",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学",
                "政治"
        ]
}
现在所有显示的人员信息里面包含语文和数学的内容。而如果差一个内容的不会显示。
虽然“$all”计算可以用于数组上，但是也可以用于一个数据的匹配上。

范例：查询位置是“成都”的人员
> db.emp.find({"loc":{"$all":["成都"]}}).pretty();
{
        "_id" : ObjectId("599108423268c8e84253be2c"),
        "name" : "郑七",
        "sex" : "女",
        "age" : 50,
        "sal" : 4700,
        "loc" : "成都"

既然在集合里面现在保存的是数组信息，那么数组就可以利用索引操作，使用“key.index”的方式来定义索引。

范例：查询课程中第二个内容（index=1，索引下标从0开始）为数学的信息
> db.emp.find({"course.1":"数学"}).pretty();
{
        "_id" : ObjectId("599129a00184ff511bf02b87"),
        "name" : "刘A",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学",
                "英语",
                "音乐",
                "政治"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b88"),
        "name" : "刘B",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b89"),
        "name" : "刘C",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学",
                "英语"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b8a"),
        "name" : "刘D",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学",
                "政治"
        ]
}

范例：要求查询出只参加两门课程的人员
使用“$size”来进行数量控制
> db.emp.find({"course":{"$size":2}}).pretty();
{
        "_id" : ObjectId("599129a00184ff511bf02b88"),
        "name" : "刘B",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学"
        ]
}
{
        "_id" : ObjectId("599129a20184ff511bf02b8b"),
        "name" : "刘E",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "政治"
        ]
}

发现在进行数据查询的时候，只要内容符合条件，数组的内容就全备显示出来，希望控制返回的数量，可以使用“$slice”进行控制。

范例：返回年龄为35岁的所有人员，但是要求只显示两门参加的课程
> db.emp.find({"age":35},{"course":{"$slice":2}}).pretty();
{
        "_id" : ObjectId("599108433268c8e84253be2d"),
        "name" : "王八",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京"
}
{
        "_id" : ObjectId("599129a00184ff511bf02b87"),
        "name" : "刘A",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b88"),
        "name" : "刘B",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b89"),
        "name" : "刘C",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b8a"),
        "name" : "刘D",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学"
        ]
}
{
        "_id" : ObjectId("599129a20184ff511bf02b8b"),
        "name" : "刘E",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "政治"
        ]
}
现在只取得了前两门的信息，那么也可以设置负数取出后两门信息。
> db.emp.find({"age":35},{"course":{"$slice":-2}}).pretty();
{
        "_id" : ObjectId("599108433268c8e84253be2d"),
        "name" : "王八",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京"
}
{
        "_id" : ObjectId("599129a00184ff511bf02b87"),
        "name" : "刘A",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "音乐",
                "政治"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b88"),
        "name" : "刘B",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "数学"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b89"),
        "name" : "刘C",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "数学",
                "英语"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b8a"),
        "name" : "刘D",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "数学",
                "政治"
        ]
}
{
        "_id" : ObjectId("599129a20184ff511bf02b8b"),
        "name" : "刘E",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "语文",
                "政治"
        ]
}
或者只是取出中间部分的信息。
> db.emp.find({"age":35},{"course":{"$slice":[1,2]}}).pretty();
{
        "_id" : ObjectId("599108433268c8e84253be2d"),
        "name" : "王八",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京"
}
{
        "_id" : ObjectId("599129a00184ff511bf02b87"),
        "name" : "刘A",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "数学",
                "英语"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b88"),
        "name" : "刘B",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "数学"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b89"),
        "name" : "刘C",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "数学",
                "英语"
        ]
}
{
        "_id" : ObjectId("599129a00184ff511bf02b8a"),
        "name" : "刘D",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "数学",
                "政治"
        ]
}
{
        "_id" : ObjectId("599129a20184ff511bf02b8b"),
        "name" : "刘E",
        "sex" : "男",
        "age" : 35,
        "sal" : 8000,
        "loc" : "北京",
        "course" : [
                "政治"
        ]
}
在此时设置的两个数据里面，第一个数据表示开始的位置，第二个数据表示个数。

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MongoDB之数据查询（数组）

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