MongoDB初探第二篇 (r4笔记第82天)
与sql语句的简单对比在第一篇中分享了一些MongoDB的基本知识点,因为安装运行其实都还是很轻巧的,所以对于大家上手来说应该问题不大,但是安装完成,数据库也可以连接了,但是MongoDB中是没有办法运行sql语句的。这个时候关系型数据库中的一些思维直接移植过来就不适用了,但是大道至简,其实道理还是相同的,对于的数据的操作可以通过api来完成,这个从某种程度上来说,是MongoDB的亮点也是另外一种优势。我简单的总结了一下常用的sql语句的一些用法在MongoDB中改怎么使用。首先一个很大的不同是,在MongoDB中,没有表的概念,都是以collection为基本的单位存储的。可以通过show collections来查看当前的数据库中存在的collections> show collectionsstartup_logsystem.indexessystem.profile我们来看看增删改查的用法。insert原本sql语句中的类似下面的语句insert into test values(100,'test1');在MongoDB中可以使用如下的方式来实现,我们多插入一些数据。db.test.insert({id:11,name:"test1"});db.test.insert({id:12,name:"test2"});db.test.insert({id:13,name:"test3"});db.test.insert({id:14,name:"test4"});db.test.insert({id:15,name:"test5"});db.test.insert({id:16,name:"test6"});查看一下数据的情况。> db.test.find();{ "_id" : ObjectId("550edf9b14fce649885d6489"), "id" : 11, "name" : "test1" }{ "_id" : ObjectId("550edf9b14fce649885d648a"), "id" : 12, "name" : "test2" }{ "_id" : ObjectId("550edf9b14fce649885d648b"), "id" : 13, "name" : "test3" }{ "_id" : ObjectId("550edf9b14fce649885d648c"), "id" : 14, "name" : "test4" }{ "_id" : ObjectId("550edf9b14fce649885d648d"), "id" : 15, "name" : "test5" }{ "_id" : ObjectId("550edf9b14fce649885d648e"), "id" : 16, "name" : "test6" }这个时候查看collections会发现,已经创建好了这个collection> show collectionsstartup_logsystem.indexessystem.profiletest还有一种插入方式,如果注意到上面的数据话,会发现有一个隐含列_id,如果需要手动指定_id列的值,可以使用save方法。> db.test.save({_id:100001,id:11,name:"test_new"})WriteResult({ "nMatched" : 0, "nUpserted" : 1, "nModified" : 0, "_id" : 100001 })查看新插入的数据,注意_id的值> db.test.find();{ "_id" : ObjectId("550edf9b14fce649885d6489"), "id" : 11, "name" : "test1" }{ "_id" : ObjectId("550edf9b14fce649885d648a"), "id" : 12, "name" : "test2" }{ "_id" : ObjectId("550edf9b14fce649885d648b"), "id" : 13, "name" : "test3" }{ "_id" : ObjectId("550edf9b14fce649885d648c"), "id" : 14, "name" : "test4" }{ "_id" : ObjectId("550edf9b14fce649885d648d"), "id" : 15, "name" : "test5" }{ "_id" : ObjectId("550edf9b14fce649885d648e"), "id" : 16, "name" : "test6" }{ "_id" : 100001, "id" : 11, "name" : "test_new" }delete如果需要删除_id为100001的列的话,可以使用如下的方法> db.test.remove({_id:100001})WriteResult({ "nRemoved" : 1 })> db.test.find();{ "_id" : ObjectId("550edf9b14fce649885d6489"), "id" : 11, "name" : "test1" }{ "_id" : ObjectId("550edf9b14fce649885d648a"), "id" : 12, "name" : "test2" }{ "_id" : ObjectId("550edf9b14fce649885d648b"), "id" : 13, "name" : "test3" }{ "_id" : ObjectId("550edf9b14fce649885d648c"), "id" : 14, "name" : "test4" }{ "_id" : ObjectId("550edf9b14fce649885d648d"), "id" : 15, "name" : "test5" }{ "_id" : ObjectId("550edf9b14fce649885d648e"), "id" : 16, "name" : "test6" }update我们尝试修改name列为test3的数据,修改id为18> db.test.update({name:"test3"},{$set:{id:18}});WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })> db.test.find();{ "_id" : ObjectId("550edf9b14fce649885d6489"), "id" : 11, "name" : "test1" }{ "_id" : ObjectId("550edf9b14fce649885d648a"), "id" : 12, "name" : "test2" }{ "_id" : ObjectId("550edf9b14fce649885d648b"), "id" : 18, "name" : "test3" }{ "_id" : ObjectId("550edf9b14fce649885d648c"), "id" : 14, "name" : "test4" }{ "_id" : ObjectId("550edf9b14fce649885d648d"), "id" : 15, "name" : "test5" }{ "_id" : ObjectId("550edf9b14fce649885d648e"), "id" : 16, "name" : "test6" }or的使用方法在sql where字句中,经常会有or这样的过滤条件我们来简单模拟一下 name为test或者name为test2的数据> db.test.find({"$or":[{name:"test1"},{name:"test2"}]}) { "_id" : ObjectId("550edf9b14fce649885d6489"), "id" : 11, "name" : "test1" }{ "_id" : ObjectId("550edf9b14fce649885d648a"), "id" : 12, "name" : "test2" }and的使用方法我们来模拟一下name为test1并且name为test2这样的数据,这样的数据应该不存在,以下是一个错误的例子。> db.test.find({name:"test1"},{name:"test2"}){ "_id" : ObjectId("550edf9b14fce649885d6489"), "name" : "test1" }正确的用法应该这么写。模拟name为test1并且id为11的数据> db.test.find({"$and":[{name:"test1"},{id:11}]}){ "_id" : ObjectId("550edf9b14fce649885d6489"), "id" : 11, "name" : "test1" }rownum> db.test.find().limit(2);{ "_id" : ObjectId("550edf9b14fce649885d6489"), "id" : 11, "name" : "test1" }{ "_id" : ObjectId("550edf9b14fce649885d648a"), "id" : 12, "name" : "test2" }count> db.test.count();6order by 注意排序的情况> db.test.find().sort({name:-1}) { "_id" : ObjectId("550edf9b14fce649885d648e"), "id" : 16, "name" : "test6" }{ "_id" : ObjectId("550edf9b14fce649885d648d"), "id" : 15, "name" : "test5" }{ "_id" : ObjectId("550edf9b14fce649885d648c"), "id" : 14, "name" : "test4" }{ "_id" : ObjectId("550edf9b14fce649885d648b"), "id" : 18, "name" : "test3" }{ "_id" : ObjectId("550edf9b14fce649885d648a"), "id" : 12, "name" : "test2" }{ "_id" : ObjectId("550edf9b14fce649885d6489"), "id" : 11, "name" : "test1" }> db.test.find().sort({name:1}) { "_id" : ObjectId("550edf9b14fce649885d6489"), "id" : 11, "name" : "test1" }{ "_id" : ObjectId("550edf9b14fce649885d648a"), "id" : 12, "name" : "test2" }{ "_id" : ObjectId("550edf9b14fce649885d648b"), "id" : 18, "name" : "test3" }{ "_id" : ObjectId("550edf9b14fce649885d648c"), "id" : 14, "name" : "test4" }{ "_id" : ObjectId("550edf9b14fce649885d648d"), "id" : 15, "name" : "test5" }{ "_id" : ObjectId("550edf9b14fce649885d648e"), "id" : 16, "name" : "test6" }in 的使用得到name在test1,test2,test3的数据 > db.test.find({'name' : {'$in' : ["test1", "test2", "test3"]}});{ "_id" : ObjectId("550edf9b14fce649885d6489"), "id" : 11, "name" : "test1" }{ "_id" : ObjectId("550edf9b14fce649885d648a"), "id" : 12, "name" : "test2" }{ "_id" : ObjectId("550edf9b14fce649885d648b"), "id" : 18, "name" : "test3" }>not in的使用> db.test.find({'name' : {'$nin' : ["test1", "test2", "test3"]}});{ "_id" : ObjectId("550edf9b14fce649885d648c"), "id" : 14, "name" : "test4" }{ "_id" : ObjectId("550edf9b14fce649885d648d"), "id" : 15, "name" : "test5" }{ "_id" : ObjectId("550edf9b14fce649885d648e"), "id" : 16, "name" : "test6" }大于等于。。的使用id大于14的数据> db.test.find({id: {$gte: 14}});{ "_id" : ObjectId("550edf9b14fce649885d648b"), "id" : 18, "name" : "test3" }{ "_id" : ObjectId("550edf9b14fce649885d648c"), "id" : 14, "name" : "test4" }{ "_id" : ObjectId("550edf9b14fce649885d648d"), "id" : 15, "name" : "test5" }{ "_id" : ObjectId("550edf9b14fce649885d648e"), "id" : 16, "name" : "test6" }like的使用 > db.test.find({name:/5/});{ "_id" : ObjectId("550edf9b14fce649885d648d"), "id" : 15, "name" : "test5" } distinctdistinct的使用,不过和sql中还是存在一定的差距,有点mapreduce的味道。> db.test.distinct('name');[ "test1", "test2", "test3", "test4", "test5", "test6" ]