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How to use $regex in MongoDB?
Following is the syntax to use $regex in MongoDB −
db.yourCollectionName.find({yourFieldName: { $regex: yourValue}});Let us first create a collection with documents −
> db.regularExpressionDemo.insertOne({"UserName":"John"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cdffc25bf3115999ed51210")
}
> db.regularExpressionDemo.insertOne({"UserName":"JOHN"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cdffc2ebf3115999ed51211")
}
> db.regularExpressionDemo.insertOne({"UserName":"john"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cdffc35bf3115999ed51212")
}
> db.regularExpressionDemo.insertOne({"UserName":"JoHn"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cdffc3ebf3115999ed51213")
}Following is the query to display all documents from a collection with the help of find() method −
> db.regularExpressionDemo.find();
This will produce the following output −
{ "_id" : ObjectId("5cdffc25bf3115999ed51210"), "UserName" : "John" }
{ "_id" : ObjectId("5cdffc2ebf3115999ed51211"), "UserName" : "JOHN" }
{ "_id" : ObjectId("5cdffc35bf3115999ed51212"), "UserName" : "john" }
{ "_id" : ObjectId("5cdffc3ebf3115999ed51213"), "UserName" : "JoHn" }Following is the query to use $regex −
> db.regularExpressionDemo.find({'UserName': { $regex: 'JOHN'}});This will produce the following output −
{ "_id" : ObjectId("5cdffc2ebf3115999ed51211"), "UserName" : "JOHN" }Let us now match all the cases. Following is the query −
> db.regularExpressionDemo.find({'UserName': { $regex: 'JOHN', $options: 'i' }});This will produce the following output −
{ "_id" : ObjectId("5cdffc25bf3115999ed51210"), "UserName" : "John" }
{ "_id" : ObjectId("5cdffc2ebf3115999ed51211"), "UserName" : "JOHN" }
{ "_id" : ObjectId("5cdffc35bf3115999ed51212"), "UserName" : "john" }
{ "_id" : ObjectId("5cdffc3ebf3115999ed51213"), "UserName" : "JoHn" }
Updated on: 30-Jul-2019
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