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MongoDB分组查询和聚合查询实例教程

作者:一恍过去

聚合(aggregate)是MongoDB的高级查询语言,它允许我们通过转化合并多个文档的数据来生成新的在单个文档里不存在的文档信息,下面这篇文章主要给大家介绍了关于MongoDB分组查询和聚合查询的相关资料,需要的朋友可以参考下

1、单一字段分组

分组后不会展示其他字段, _id为固定写法,userid为分组字段

# 比如对比sql:select userid from testgroup by userid
db.test.aggregate({"$group":{"_id":"$userid"}} )

效果:

2、多字段分组

_id为固定写法,userid与articleid为分组字段,多字段时需要设置一个别名

# 比如对比sql:select userid,articleid from testgroup by userid,articleid
db.test.aggregate({"$group":{"_id":{"userid":"$userid","articleid":"$articleid"}}})

效果:

3、条件匹配分组

$match表示匹配条件,在group前表示where,在后表示having,userid为分组字段

# 比如对比sql:select userid from testwhere userid in("1","2")  group by userid
db.test.aggregate(
    {"$match":{"userid":{"$in":["1","2"]}}},
    {"$group":{"_id":"$userid"}}
)
或者
# 比如对比sql:select userid,articleid from test where userid in("1","2")  group by userid
db.test.aggregate(
    {"$match":{"userid":{"$in":["1","2"]}}},
    {"$group":{"_id":{"userid":"$userid","articleid":"$articleid"}}}
)
或者having聚合查询
# 比如:select userid,avg(price) as avg from test where userid >'10' group by userid having avg>35
db.test.aggregate(
    {"$match":{"userid":{"$gt":"10"}}},
    {"$group":{"_id":"$userid",'avg':{"$avg":"$price"}}},
    {"$match":{"avg":{"$gt":35}}}
)

效果:

4、分组分页排序

限制:$limit、跳过:$skip

db.test.aggregate(
        {"$group":{"_id":"$userid"}},
        {"$skip":1},
        {"$limit":2}
	)

5、聚合分组

聚合分组,分为:$sum、$avg、$max、$min、$first、$last,聚合结果需要使用别名,并且可以结合条件和排序等元素

为了测试聚合,增加一下文件:

    db.test.insert([{
        "articleid":"1",
        "price":200,
        "userid":"5"
    },{
        "articleid":"2",
        "price":300,
        "userid":"5"
    },{
        "articleid":"3",
        "price":400,
        "userid":"5"
    },{
        "articleid":"1",
        "price":200,
        "userid":"6"
    },{
        "articleid":"2",
        "price":300,
        "userid":"7"
    }]);

5.1、sum聚合-求数值总和

求某个数值总和,userid分组字段[可以用于多字段聚合],{"$sum":$price}表示求price合计

db.test.aggregate({"$group":{"_id":"$userid","total":{"$sum":"$price"}}})

5.2、sum聚合-求分组后数量

db.test.aggregate({"$group":{"_id":"$userid","total":{"$sum":1}}})

效果:

5.3、avg、max、min聚合

avg、max、min可以分开使用,也可以一起使用

db.test.aggregate({"$group":{"_id":"$userid","avg":{"$avg":"$price"},"max":{"$max":"$price"},"min":{"$min":"$price"}}})

效果:

5.4、复合聚合

可以多字段聚合求值,通过sumavg、max、min进行组合

db.test.aggregate({"$group":{"_id":"$userid"
	,"total":{"$sum":"$price"}
	,"avg":{"$avg":"$price"}}})

效果:

5.5、聚合分组排序

对聚合结果进行排序,$sort-排序,avg-聚合结果的别名,1:升序,-1:降序

# 先按userid降序,再avg升序
	db.test.aggregate({"$group":{"_id":"$userid"
	,"avg":{"$avg":"$price"}}}
	,{"$sort":{"avg":1}}
	,{"$sort":{"_id":-1}})

效果:

5.6、首尾取值聚合

$first-第一个元素、$last-最后一个元素

vdb.test.aggregate({"$group":{"_id":"$userid","prices":{"$first":"$price"}}})

效果:

5.7、聚合分组拼接

等同于group_concat,$push-元素可重复,$addToSet-元素不可重复,将分组后的数据拼接为一个数组

db.test.aggregate({"$group":{"_id":"$userid","names":{"$push":"$price"}}})

效果:

补充:关于MongoDB中一些复杂的聚合分组查询操作

一、字段切割&条件判断

汇总各个店铺【$shop_name】在某个时间段【$patrol_time】内违规【$whether_violates == ‘Y’】的记录数

1.$substr:[‘字段名’,开始下标,结束下标]

2.$cond:{if…then…else}

查询SQL如下:

db.t_tbshop_patrol.aggregate([
    {
        "$project": 
        {
            "yearMonthDay": {
                "$substr": ["$patrol_time", 0, 10]
            },
            "patrol_time": 1,
            "shop_name": 1,
            "whether_violates": 1,
            "y_count": {
                "$sum": {
                    "$cond": {
                        "if": {
                            "$eq": ["$whether_violates", "Y"]
                        },
                        "then": 1,
                        "else": 0
                    }
                }
            }
        }
    },
    {
        "$match": {
            "patrol_time": {
                "$gte": "2021-09-29 00:00:00",
                "$lte": "2021-09-29 23:59:59"
            }
        }
    },
    {
        "$group": {
            "_id": {
                "patrol_time": "$yearMonthDay",
                "shop_name": "$shop_name"
            },
            "violate_y": {
                "$sum": "$y_count"
            }
        }
    },
    /* 只展示汇总结果大于0的店铺数据,去掉下面{'$match'}则展示所有店铺数据 */
    {
        "$match": {
            "violate_y": {
                "$gt": 0
            }
        }
    }
])

查询结果如下:

/* 1 */
{
    "_id" : {
        "patrol_time" : "2021-09-29",
        "shop_name" : "VETA个护海外旗舰店"
    },
    "violate_y" : 5.0
}

/* 2 */
{
    "_id" : {
        "patrol_time" : "2021-09-29",
        "shop_name" : "swisseFuJun海外专卖店"
    },
    "violate_y" : 24.0
}

/* 3 */
{
    "_id" : {
        "patrol_time" : "2021-09-29",
        "shop_name" : "咿儿润旗舰店"
    },
    "violate_y" : 1.0
}

二、联表查询&类型转换&拆分数组

根据日期查询订单表中每条订单数据每种商品(非赠品)的总金额(业务需要显示仓库,但原始数据中只有仓库编号,所以和仓库信息表【t_warehouse_info】使用联表查询)

1.$lookup

2.$toDouble、$convert

3.$unwind

原始数据示例:

{
    "_id" : ObjectId("5f33abcdfc12b1f2d21b2e5d"),
    /* 订单编号 */
    "order_sn" : "12023232223920",
    "add_time" : "2021-09-29 20:01:25",
    "complete_time" : "1596330674",
     /* 仓库编号 */
    "fhck" : "151",
    "last_update" : "2021-09-29 09:14:03",
    "lylx" : "1",
    /* 订单商品明细:同一笔订单下的同一商品可能有多条,所以需要根据商品编号【goods_sn】分组求和 */
    "orderDetailGets" : [ 
        {
            "goods_sn" : "6925425422173",
            "goods_id" : "2518",
            "goods_number" : "3",
            "goods_price" : "35.19",
            "shop_price" : "79.00",
            "share_price" : "35.19",
             /* 支付金额 */
            "share_payment" : "35.19",
            "original_order_sn" : "12023232223920",
            "goods_name" : "口力橡皮糖500g",
            /* 是否赠品(1:是;0:否)*/
            "is_gift" : "0",
            "share_shipping_fee" : "0.00"
        }, 
        {
            "goods_sn" : "6971083865227",
            "goods_id" : "1569",
            "goods_number" : "1",
            "goods_price" : "1.87",
            "shop_price" : "4.50",
            "share_price" : "1.87",
            "share_payment" : "1.87",
            "original_order_sn" : "12023232223920",
            "goods_name" : "口力组合橡皮糖随手包30g",
            "is_gift" : "0",
            "share_shipping_fee" : "0.00"
        }, 
        {
            "goods_sn" : "6971083865227",
            "goods_id" : "1569",
            "sku_id" : "1569",
            "goods_number" : "2",
            "goods_price" : "1.87",
            "shop_price" : "4.50",
            "goods_price" : "1.87",
            "share_payment" : "3.74",
            "original_order_sn" : "12023232223920",
            "goods_name" : "口力组合橡皮糖随手包30g",
            "is_gift" : "0",
            "share_shipping_fee" : "0.00"
        }
    ],
    "order_msg" : "",
    "order_status" : "5",
    "pay_time" : "2021-09-29 20:03:13",
    "payment" : "37.06",
    "sd_name" : "口力旗舰店",
    "total_amount" : "84.54",
    "weigh" : "0.800000"
}

查询SQL如下:

db.getCollection('t_shop_order').aggregate([
    {
        "$match": {
            "add_time": {
                "$gte": "2021-12-14 00:00:00",
                "$lte": "2021-12-14 23:59:59"
            }
        }
    },
    /* $lookup联表查询:相当于left join;关联后的子表数据无论是1对1还是1对多,都会形成一个数组对象 */
    {
        "$lookup": {
            "from": "t_warehouse_info",
            /* 主表的关联字段名 */
            "localField": "fhck",
            /* 关联表的字段名 */
            "foreignField": "ckdm",
            /* 关联表别名,作为数据的字段名 */
            "as": "warehouse_info"
        }
    },
    /* $unwind拆分数组对象,扁平化展示 */
    {
        "$unwind": "$orderDetailGets"
    },
    {
        "$project": {
            "order_sn": 1,
            "add_time": 1,
            "goods_sn": "$orderDetailGets.goods_sn",
            "is_gift": "$orderDetailGets.is_gift",
            /* $convert类型转换:将字符串转换为int类型,以助于后面的数据统计 */
            "goods_number": {
                "$convert": {
                    "input": "$orderDetailGets.goods_number",
                    "to": "int"
                }
            },
            "goods_name": "$orderDetailGets.goods_name",
            /* $ifNull空判断:如果对应字符串为null,则设置默认值为0 */
            /* $toDouble转换为浮点型:将数据转换为浮点型数据 */
            "share_payment": {
                "$ifNull": [{
                    "$toDouble": "$orderDetailGets.share_payment"
                }, 0]
            },
            "ckmc": "$warehouse_info.ckmc"
        }
    },
    {
        "$match": {
            "is_gift": "0"
        }
    },
    {
        "$unwind": "$ckmc"
    },
    {
        "$group": {
            _id: {
                "order_sn": "$order_sn",
                "add_time": "$add_time",
                "goods_sn": "$goods_sn",
                "goods_name": "$goods_name"
            },
            "goods_number": {
                "$sum": "$goods_number"
            },
            "share_payment": {
                "$sum": "$share_payment"
            }
        }
    }
])

查询SQL如下:

/* 1 */
{
    "_id" : {
        "order_sn" : "12023232223920",
        "add_time" : "2021-12-14 12:22:16",
        "goods_sn" : "6925425422173",
        "goods_name" : "口力橡皮糖500g"
    },
    "goods_number" : 3,
    "share_payment" : 35.19
}
/* 2 */
{
    "_id" : {
        "order_sn" : "12023232223920",
        "add_time" : "2021-12-14 22:37:09",
        "goods_sn" : "6971083865227",
        "goods_name" : "口力组合橡皮糖随手包30g"
    },
    "goods_number" : 3,
    "share_payment" : 5.61
}

总结

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