The find() Method
To query data from MongoDB collection, you need to use MongoDB's find() method.
Syntax
Basic syntax of find() method is as follows
>db.COLLECTION_NAME.find()
find() method will display all the documents in a non structured way.
The pretty() Method
To display the results in a formatted way, you can use pretty() method.
Syntax:
>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.tutorialspoint.com",
"tags": ["mongodb", "database", "NoSQL"],
"likes": "100"
}
>
Apart from find() method there is findOne() method, that reruns only one document.
RDBMS Where Clause Equivalents in MongoDB
To query the document on the basis of some condition, you can use following operations
| Operation | Syntax | 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:50}}).pretty() | where likes < 50 |
| Less Than Equals | {<key>:{$lte:<value>}} | db.mycol.find({"likes":{$lte:50}}).pretty() | where likes <= 50 |
| Greater Than | {<key>:{$gt:<value>}} | db.mycol.find({"likes":{$gt:50}}).pretty() | where likes > 50 |
| Greater Than Equals | {<key>:{$gte:<value>}} | db.mycol.find({"likes":{$gte:50}}).pretty() | where likes >= 50 |
| Not Equals | {<key>:{$ne:<value>}} | db.mycol.find({"likes":{$ne:50}}).pretty() | where likes != 50 |
AND in MongoDB
Syntax:
In the find() method if you pass multiple keys by separating them by ',' then MongoDB treats it AND condition. Basic syntax of AND is shown below:
>db.mycol.find({key1:value1, key2:value2}).pretty()
Example
Below given example will show all the tutorials written by 'tutorials point' and whose title is '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": "tutorials point",
"url": "http://www.tutorialspoint.com",
"tags": ["mongodb", "database", "NoSQL"],
"likes": "100"
}
>
For the above given example equivalent where clause will be ' where by='tutorials point' AND title='MongoDB Overview' '. You can pass any number of key, value pairs in find clause.
OR in MongoDB
Syntax:
To query documents based on the OR condition, you need to use $or keyword. Basic syntax of OR is shown below:
>db.mycol.find(
{
$or: [
{key1: value1}, {key2:value2}
]
}
).pretty()
Example
Below given example will show all the tutorials written by 'tutorials point' or whose title is 'MongoDB Overview'
>db.mycol.find({$or:[{"by":"tutorials point"},{"title": "MongoDB Overview"}]}).pretty()
{
"_id": ObjectId(7df78ad8902c),
"title": "MongoDB Overview",
"description": "MongoDB is no sql database",
"by": "tutorials point",
"url": "http://www.tutorialspoint.com",
"tags": ["mongodb", "database", "NoSQL"],
"likes": "100"
}
>
Using AND and OR together
Example
Below given example will show the documents that have likes greater than 100 and whose title is either 'MongoDB Overview' or by is 'tutorials point'. Equivalent sql where clause is'where likes>10 AND (by = 'tutorials point' OR title = 'MongoDB Overview')'
>db.mycol.find({"likes": {$gt:10}, $or: [{"by": "tutorials point"},{"title": "MongoDB Overview"}]}).pretty()
{
"_id": ObjectId(7df78ad8902c),
"title": "MongoDB Overview",
"description": "MongoDB is no sql database",
"by": "tutorials point",
"url": "http://www.tutorialspoint.com",
"tags": ["mongodb", "database", "NoSQL"],
"likes": "100"
}
>
