MongoDB的查询数组

MongoDB的查询数组

MongoDB查询数组学习笔记

首先我们先插入几个文档

> db.food.insert({“_id”:1, “fruit”:["apple","banana","peach"]})
> db.food.insert({“_id”:2, “fruit”:["apple","kumquat","orange"]})
> db.food.insert({“_id”:3, “fruit”:["cherry","banana","apple"]})

我们想要查询既包含”apple”并且又包含”banana”的文档，就需要使用”$all“来查询

> db.food.find({“fruit”:{“$all”:["apple","banana"]}})
{ “_id” : 1, “fruit” : [ "apple", "banana", "peach" ] }
{ “_id” : 3, “fruit” : [ "cherry", "banana", "apple" ] }

还记得之前的”$in“吗，如果我们需要查询包含”apple”或者”banana”的文档，则使用”$in”

> db.food.find({“fruit”:{“$in”:["apple","banana"]}})
{ “_id” : 1, “fruit” : [ "apple", "banana", "peach" ] }
{ “_id” : 2, “fruit” : [ "apple", "kumquat", "orange" ] }
{ “_id” : 3, “fruit” : [ "cherry", "banana", "apple" ] }

使用”$size“可以查询指定长度的数组

> db.food.find({“fruit”:{$size:3}})
{ “_id” : 1, “fruit” : [ "apple", "banana", "peach" ] }
{ “_id” : 2, “fruit” : [ "apple", "kumquat", "orange" ] }
{ “_id” : 3, “fruit” : [ "cherry", "banana", "apple" ] }

使用”$slice“返回数组中的一个子集合

> db.blog.findOne()
{
    ”_id” : ObjectId(“4e914ad2717ed94f8289ac08″),
    ”comments” : [
        {
            "name" : "joe",
            "email" : "[e-mail]",
            "content" : "good blog"
        },
        {
            "content" : "Changed Comment",
            "email" : "[e-mail]",
            "name" : "john"
        },
        {
            "name" : "test",
            "email" : "[e-mail]",
            "content" : "test"
        },
        {
            "name" : "test1",
            "email" : "[e-mail]",
            "content" : "test1"
        },
        {
            "name" : "test12",
            "email" : "[e-mail]",
            "content" : "test12"
        },
        {
            "name" : "test123",
            "email" : "[e-mail]",
            "content" : "test123"
        }
    ],
    ”content” : “My first blog.”,
    ”title” : “Hello World”
}

需要返回comments中的前两条数据，如下查询语句

> db.blog.findOne({},{“comments”:{$slice:2}})
{
    ”_id” : ObjectId(“4e914ad2717ed94f8289ac08″),
    ”comments” : [
        {
            "name" : "joe",
            "email" : "[e-mail]",
            "content" : "good blog"
        },
        {
            "content" : "Changed Comment",
            "email" : "[e-mail]",
            "name" : "john"
        }
    ],
    ”content” : “My first blog.”,
    ”title” : “Hello World”
}

查询comments中后两条数据的查询语句：

> db.blog.findOne({},{“comments”:{$slice:-2}})

还可以返回跳过几个文档之后的几个文档

> db.blog.findOne({},{“comments”:{$slice:[1,2]}})
{
    ”_id” : ObjectId(“4e914ad2717ed94f8289ac08″),
    ”comments” : [
        {
            "content" : "Changed Comment",
            "email" : "[e-mail]",
            "name" : "john"
        },
        {
            "name" : "test",
            "email" : "[e-mail]",
            "content" : "test"
        }
    ],
    ”content” : “My first blog.”,
    ”title” : “Hello World”
}