MongoDB Query Document

MongoDB versus RDBMS Where statement comparison

Operation	format	Example	similar statements in an RDBMS
Equals	{<key>:<value>}	db.col.find({"by":"XXXX"}).pretty()	where by = ‘XXXX‘
Less than	{<key>:{$lt:<value>}}	db.col.find({"likes":{$lt:50}}).pretty()	where likes < 50
Less than or equal to	{<key>:{$lte:<value>}}	db.col.find({"likes":{$lte:50}}).pretty()	where likes <= 50
Greater than	{<key>:{$gt:<value>}}	db.col.find({"likes":{$gt:50}}).pretty()	where likes > 50
Greater than or equal to	{<key>:{$gte:<value>}}	db.col.find({"likes":{$gte:50}}).pretty()	where likes >= 50
Not equal to	{<key>:{$ne:<value>}}	db.col.find({"likes":{$ne:50}}).pretty()	where likes != 50

MongoDB and condition

The MongoDB find () method can pass in multiple keys (key), each separated by commas, which is the and condition of the regular SQL.

The syntax format is as follows:

DB col   find   ({ key1  :  value1    Key2  :  value2  }) . pretty   ()  
               

MongoDB OR Condition

DB.Col.Find( {$or: [     {Key1:value1},   { key2  :  value2  }   ]   }  ).  pretty   () 
 
  Example: 
 db.getcollection (' products '). Find ({$or: [{"_id": "Xclient_ Jiyinshuoxilie "}, {" _id ":" Changdaokang_meiyinjiyin "}]}). Pretty ()  
      

Combined with and OR

DB.  Col.  Find({"likes":{$gt:-}, $or:[{"by":" Xxxxxxxxxx "},{" title ":" MongoDB XXXXXX "}]}).  Pretty()                 

MongoDB Query Document