Mongodb-数组查询

tingcheng

1.$all

如果需要对数组中的多个元素进行匹配查询，就要用到$all 如下创建一个包含三个元素的集合：

>db.product.insert(
    {
        "_id":ObjectId("4b5d85546de654d8ee55462"),
       "productno":
        [    "2020110",
             "2020111",
             "2020112"
        ] 
    }
)

>db.product.insert(
    {
        "_id":ObjectId("4e3d85546de654d8ee55962"),
       "productno":
        [    "2020110",
             "2020113",
             "2020114"
        ] 
    }
)

>db.product.insert(
    {
        "_id":ObjectId("4e3u85546de654d8ee48862"),
       "productno":
        [    "2020115",
             "2020111",
             "2020110"
        ] 
    }
)

现在要找到既有 2020110又有2020111的文档

>db.product.find({productno:{$all:["2020110","2020111"]}})
{    
    "_id":ObjectId("4b5d85546de654d8ee55462"),
    "productno":
      [    "2020110",
           "2020111"
           "2020112"
    ]
},
{    
      "_id":ObjectId("4e3u85546de654d8ee48862") ,
      "productno":
        [
            ""2020115,
            "2020111",
            "2020110"
        ]
}

2.$slice

此操作符可以返回某个键匹配数组元素的一个子集,指定数组的长度

>db.sonum.findOne()
{
    "_id":ObjectId("56de5e24et65ddf36r85"),
    sonumber:
        [
            "a01",
            "a02",
            "a03",
            "a04",
            "a05",
            "a06"
        ]
}

想要返回前5个订单号，可以如下操作

>db.sonum.findOne({"_id":ObjectId("56de5e24et65ddf36r85"},{"sonumber""{"$slice":5}})
  {
    "_id":ObjectId("56de5e24et65ddf36r85"),
    "sonumber":
        [
            "a01",
            "a02",
            "a03",
            "a04",
            "a05"
        ]
}

$slice常与$push一起使用，限制数组的总长度，$slice -5说明数组的长度为5，如果再$push两个元素进行 $slice -5操作

>db.sonum.update({"_id":ObjectId("56de5e24et65ddf36r85"},{"$push":{"sonumber":{"$each":["A07","A08"],"$slice":-5}}})

>db.sonum.findOne({"_id":ObjectId("56de5e24et65ddf36r85"},{"sonumber""{"$slice":-5}})
  {
    "_id":ObjectId("56de5e24et65ddf36r85"),
    "sonumber":
        [
            "a04",
            "a05",
            "a06"，
            "a07",
            "a08"
        ]
}

返回最后的5个元素["a04","a05","a06","a07","a08"],如果是$slice:5,则返回["a01","a02","a03","a04","a05"]