mongodb要如何去查询数据
MongoDB要如何去查询数据？针对这个问题，这篇文章详细介绍了相对应的分析和解答，希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。
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1、插入测试数据
use flower
db.goods.insert({'goods_name':'Hyacinth',price:10,num:800})
db.goods.insert({goods_name:'Hyacinth',price:10,num:800})
db.goods.insert({goods_name:'violet',price:20,num:1000})
db.goods.insert({goods_name:'Plum blossom',price:20,num:1000})
db.goods.insert({goods_name:'Datura',price:40,num:700})
db.goods.insert({goods_name:'Rosemary',price:39,num:2000})
db.goods.insert({goods_name:'Rosemary',price:39,num:2000,area:{province:'beijing','city':'beijing'}})
db.goods.insert({goods_name:'Rosemary',price:39,num:2000,area:{province:'Shanghai','city':'Shanghai'}})
db.goods.insert({goods_name:'Chinese rose',price:67,num:3700,area:{province:'Henan','city':'Luoyang'}})
db.goods.insert({goods_name:'Chinese rose',price:32,num:900,area:{province:'Henan','city':'Luoyang'}})
db.goods.insert({goods_name:'Chinese rose',price:32,num:900,area:{province:'Henan','city':'Luoyang'},color:
['write','red']})
db.goods.insert({goods_name:'Chinese rose',price:32,num:900,area:{province:'Henan','city':'Luoyang'},color:
['red','green']})
db.goods.insert({goods_name:'Chinese rose',price:32,num:900,area:{province:'Henan','city':'Luoyang'},color:
['write','red','grees']})添加数据的方式：普通数据的添加、多维数据的添加、数组数据的添加
2、MongoDB命令行查询数据
MongoDB命令行查询数据有以下几种方式：
·笼统方式查询
·条件限制查询
·范围查询
·多个查询条件
·多维字段的查询
·数组条件的限制查询
·字段的限制查询
1）笼统方式查询：
db.goods.find()
db.goods.find()
{ "_id" : ObjectId("5cb5bba28a0ad00bec55f14b"), "goods_name" : "Hyacinth", "price" : 10, "num" : 800 }
{ "_id" : ObjectId("5cb5bba28a0ad00bec55f14c"), "goods_name" : "Hyacinth", "price" : 10, "num" : 800 }
{ "_id" : ObjectId("5cb5bba28a0ad00bec55f14d"), "goods_name" : "violet", "price" : 20, "num" : 1000 }
……采用这种方式查询，会查询所有数据。
db.goods.findOne()
查询所有数据中的第一条，并且将数据格式化输出。
db.goods.findOne()
{
"_id" : ObjectId("5cb5bba28a0ad00bec55f14b"),
"goods_name" : "Hyacinth",
"price" : 10,
"num" : 800
}2）条件限制查询
db.goods.find({goods_name:'Hyacinth'}){ "_id" : ObjectId("5cb5bba28a0ad00bec55f14b"), "goods_name" : "Hyacinth", "price" : 10, "num" : 800 }
{ "_id" : ObjectId("5cb5bba28a0ad00bec55f14c"), "goods_name" : "Hyacinth", "price" : 10, "num" : 800 }相当于：SELECT *FROM goods WHERE goods_name='Hyacinth'
db.goods.findOne({goods_name:'Hyacinth'}){
"_id" : ObjectId("5cb5bba28a0ad00bec55f14b"),
"goods_name" : "Hyacinth",
"price" : 10,
"num" : 800
}该_id字段的内容值是MongoDB本身算法获得出来的，_id字段对应的值是“全球唯一”的，相当于MySQL表里的主键id，是唯一的。id可以自行设置，但是不推荐。
优点：方便MongoDB的数据做升级、迁移
3）范围查询
查询goods表中价格大于10的数据：
db.goods.find({price:{'$gt':10}})查询goods表中价格大于等于10的数据：
db.goods.find({price:{'$gte':10}})查询goods表中价格小于10的数据：
db.goods.find({price:{'$lt':12}})查询goods表中价格小于等于10的数据：
db.goods.find({price:{'$lte':12}})4）多个查询条件
例如：要求price大于10，库存大于800
db.goods.find({price:{'$gt':10},num:{'$gt':800}})要求price大于10，库存为900
db.goods.find({price:{'$gt':10},num:900})5）多维字段的查询
db.goods.find({'area.province':'Shanghai'})db.goods.find({'area.city':'Shanghai'})6）数组条件的限制查询
查询“color”中有“red”记录，满足一个元素即可：
db.goods.find({color:'red'})查询“color”中有“red”并且(AND)有“write”的记录：
db.goods.find({color:{'$all':['red','write']}})查询“price”是10或者(OR)“num”是800
db.goods.find({$or:[{'price':10},{'num':800}]})7）字段的限制查询
db.goods.find({price:32},{goods_name:1}){ "_id" : ObjectId("5cb5bba28a0ad00bec55f154"), "goods_name" : "Chinese rose" }
{ "_id" : ObjectId("5cb5bba28a0ad00bec55f155"), "goods_name" : "Chinese rose" }
{ "_id" : ObjectId("5cb5bba28a0ad00bec55f156"), "goods_name" : "Chinese rose" }
{ "_id" : ObjectId("5cb5bba48a0ad00bec55f157"), "goods_name" : "Chinese rose" }db.goods.find({price:32},{goods_name:1,_id:0}){ "goods_name" : "Chinese rose" }
{ "goods_name" : "Chinese rose" }
{ "goods_name" : "Chinese rose" }
{ "goods_name" : "Chinese rose" }db.goods.find({price:{'$gt':30}},{goods_name:1,_id:0}){ "goods_name" : "Datura" }
{ "goods_name" : "Rosemary" }
{ "goods_name" : "Rosemary" }
{ "goods_name" : "Rosemary" }
{ "goods_name" : "Chinese rose" }
{ "goods_name" : "Chinese rose" }
{ "goods_name" : "Chinese rose" }
{ "goods_name" : "Chinese rose" }
{ "goods_name" : "Chinese rose" }db.goods.find({price:{'$gt':30}},{goods_name:1,price:1,_id:0}){ "goods_name" : "Datura", "price" : 40 }
{ "goods_name" : "Rosemary", "price" : 39 }
{ "goods_name" : "Rosemary", "price" : 39 }
{ "goods_name" : "Rosemary", "price" : 39 }
{ "goods_name" : "Chinese rose", "price" : 67 }
{ "goods_name" : "Chinese rose", "price" : 32 }
{ "goods_name" : "Chinese rose", "price" : 32 }
{ "goods_name" : "Chinese rose", "price" : 32 }
{ "goods_name" : "Chinese rose", "price" : 32 }说明：_id字段除外，其它字段可以随意设置0，1。可以设置全部字段都输出，也设置为全部字段都不输出。但是，字段中一个是1，另一个是0，这是不可以。
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