MongoDB Tutorial Lesson Seventh MongoDB Query Document

Find () method

To query the collection data from MongoDB, you need to use the MongoDB find () method.

Grammar

The basic find () method syntax is as follows

>db.  Collection_name.  Find()     

The Find () method displays all the files in an unstructured manner.

Pretty () method

The results are displayed in a formatted manner and can be used with the pretty () method.

Grammar:

>db.  MyCol.  Find().  Pretty()       

Example

>Db.MyCol.Find().Pretty(){ "_ID": ObjectId(7df78ad8902c), "Title": "MongoDB Overview", "description": "MongoDB is no SQL database",  "by" :  " Tutorials Point ", " url ":   "http://www.yiibai.com" , "tags" : [ "MongoDB" Span class= "pun" >,  "database" , "NoSQL" ],  "likes" :< Span class= "PLN" >  "
                                                            
                                                             }>   
                                                                         

In addition to the find () method, there is a FindOne () method that returns a file.

RDBMS WHERE clause and MongoDB equivalent statement

To query the file based on some conditions, you can use the following actions

Operation	Grammar	Example	RDBMS equivalent
Equality	{<key>:<value>}	Db.mycol.find ({"By": "Tutorials Point"}). Pretty ()	where by = ' tutorials point '
Less Than	{<key>:{$lt: <value>}}	Db.mycol.find ({"likes": {$lt:). Pretty ()	Where likes < 50
Less Than Equals	{<key>:{$lte: <value>}}	Db.mycol.find ({"likes": {$lte:). Pretty ()	where likes <= 50
Greater Than	{<key>:{$gt: <value>}}	Db.mycol.find ({"likes": {$gt:). Pretty ()	where likes > 50
Greater Than Equals	{<key>:{$gte: <value>}}	Db.mycol.find ({"likes": {$gte:). Pretty ()	where likes >= 50
Not Equals	{<key>:{$ne: <value>}}	Db.mycol.find ({"likes": {$ne:). Pretty ()	where likes! = 50

And in MongoDB usage syntax:

In the Find () method, if you detach ', ' through multiple keys, then MongoDB handles the and condition. The and basic syntax is as follows:

>db.  MyCol.  Find({key1:value1, key2:value2}).  Pretty()               

Example

The examples given below will show all tutorials, titled "MongoDB Overview"

>Db.MyCol.Find({"By":"Tutorials Point","Title": "MongoDB Overview"}).Pretty(){ "_ID": ObjectId(7df78ad8902c), "Title": "MongoDB Overview", "description": "MongoDB is no SQL database",  "by" :  " Yiibai ", " url ":  "http://www.yiibai.com" ,  "tags" : [ "MongoDB" ,  "database" ,  "NoSQL"    "likes" :  "
                                                                         
                                                                          }>    
                                                                            

For the example given above is equivalent to the WHERE clause ' where by= ' Yiibai ' and title= ' MongoDB Overview ', can pass any number of key-value pairs in the Find clause.

MongoDB in or syntax:

To query a file based on the or condition, you need to use the $or keyword. The OR basic syntax is as follows:

>db.  MyCol.  Find({ $or:[{key1: value1},{key2:value2} ]}). Pretty()                 

Example

The examples given below will show all tutorials, written by ' Yiibai ' or titled "MongoDB Overview"

>Db.MyCol.Find({$or:[{"By":"Yiibai"},{"Title": "MongoDB Overview"}]}).Pretty(){ "_ID": ObjectId(7df78ad8902c), "Title": "MongoDB Overview", "description": "MongoDB is no SQL database",  "by" :  " Yiibai ", " url ":  "http://www.yiibai.com" ,  "tags" : [ "MongoDB" ,  "database" ,  "NoSQL"    "likes" :  "
                                                                           
                                                                            }>    
                                                                              

Use examples with and and OR

The example given below will show a file with the image greater than 100, with the title "MongoDB Overview" or "Yiibai". Equivalent to the SQL WHERE clause for ' where likes>10 and (by = ' Yiibai ' OR title = ' MongoDB Overview ') '

>Db.MyCol.Find("Likes": {$gt:10},$or: [{"By": "Yiibai"}, {"Title": "MongoDB Overview"}] }).Pretty(){ "_ID": ObjectId(7df78ad8902c), "Title": "MongoDB Overview", "description": "MongoDB is no SQL database",  "by" :  " Yiibai ", " url ":  "http://www.yiibai.com" ,  "tags" : [ "MongoDB" ,  "database" ,  "NoSQL"    "likes" :  "
                                                                                          
                                                                                           }>    
                                                                                             

MongoDB Tutorial Seventh lesson MongoDB querying document