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