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MongoDB query condition to compare two fields?
You can use $where operator along with find() method to compare two fields in MongoDB. The syntax is as follows:
db.yourCollectionName.find({$where:”yourCondition”}).pretty();To understand the above syntax, let us create a collection with some documents. The query to create a collection with documents is as follows:
>db.compareTwoFields.insert({"Id":1,"FullName":{"FirstName":"John","LastName":"Smith"},
"BranchName":"ComputerScience"});
WriteResult({ "nInserted" : 1 })
>db.compareTwoFields.insert({"Id":2,"FullName":{"FirstName":"Smith","LastName":"Smith"},
"BranchName":"Civil"});
WriteResult({ "nInserted" : 1 })
>db.compareTwoFields.insert({"Id":3,"FullName":{"FirstName":"David","LastName":"Smith"},
"BranchName":"Mechanical"});
WriteResult({ "nInserted" : 1 })Now you can display all documents from a collection with the help of find() method. The query is as follows:
> db.compareTwoFields.find().pretty();
The following is the output:
{
"_id" : ObjectId("5c6c237568174aae23f5ef64"),
"Id" : 1,
"FullName" : {
"FirstName" : "John",
"LastName" : "Smith"
},
"BranchName" : "ComputerScience"
}
{
"_id" : ObjectId("5c6c239868174aae23f5ef65"),
"Id" : 2,
"FullName" : {
"FirstName" : "Smith",
"LastName" : "Smith"
},
"BranchName" : "Civil"
}
{
"_id" : ObjectId("5c6c23b468174aae23f5ef66"),
"Id" : 3,
"FullName" : {
"FirstName" : "David",
"LastName" : "Smith"
},
"BranchName" : "Mechanical"
}The following is the query to compare two fields in MongoDB:
>db.compareTwoFields.find({$where:"this.FullName.FirstName==this.FullName.LastName"}).
pretty();The following is the output:
{
"_id" : ObjectId("5c6c239868174aae23f5ef65"),
"Id" : 2,
"FullName" : {
"FirstName" : "Smith",
"LastName" : "Smith"
},
"BranchName" : "Civil"
}
Updated on: 30-Jul-2019
4K+ Views
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