MongoDB语法与现有关系型数据库SQL语法比较
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MongoDB语法 mysql语法
db.test.find(‘name‘:‘foobar‘) <==> select * from test where name=‘foobar‘
db.test.find() <==> select *from test
db.test.find(‘ID‘:10).count() <==> select count(*) from test where ID=10
db.test.find().skip(10).limit(20) <==> select * from test limit 10,20
db.test.find(‘ID‘:$in:[25,35,45]) <==> select * from test where ID in (25,35,45)
db.test.find().sort(‘ID‘:-1) <==> select * from test order by IDdesc
db.test.distinct(‘name‘,‘ID‘:$lt:20) <==> select distinct(name) from testwhere ID<20
db.test.group(key:‘name‘:true,cond:‘name‘:‘foo‘,reduce:function(obj,prev)prev.msum+=obj.marks;,initial:msum:0) <==> select name,sum(marks) from testgroup by name
db.test.find(‘this.ID<20‘,name:1) <==> select name from test whereID<20
db.test.insert(‘name‘:‘foobar‘,‘age‘:25) <==> insertinto test (‘name‘,‘age‘) values(‘foobar‘,25)
db.test.remove() <==> delete * from test
db.test.remove(‘age‘:20) <==> delete test where age=20
db.test.remove(‘age‘:$lt:20) <==> delete test where age<20
db.test.remove(‘age‘:$lte:20) <==> delete test where age<=20
db.test.remove(‘age‘:$gt:20) <==> delete test where age>20
db.test.remove(‘age‘:$gte:20) <==> delete test where age>=20
db.test.remove(‘age‘:$ne:20) <==> delete test where age!=20
db.test.update(‘name‘:‘foobar‘,$set:‘age‘:36) <==> update test set age=36 where name=‘foobar‘
db.test.update(‘name‘:‘foobar‘,$inc:‘age‘:3) <==> update test set age=age+3 where name=‘foobar‘
模糊查询：$regex
db.test.find("name":$regex:"aaa")
分组个数过滤
db.getCollection(‘id_mapper‘).aggregate([$group: _id :"$contract_id",count:$sum:1,$match:count:$gt:1])
判断是否为空
db.getCollection(‘id_mapper‘).find("sinocardid":$in:[null])
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