$concat Operator - (MongoDB Misc)

In this page, we will discuss the $concat operator in MongoDB. We will cover its syntax, example, output, explanation, use, important points, and summary.

Syntax

The $concat operator in MongoDB is used to concatenate strings. The syntax for $concat operator is as follows:

{ $concat: [ <string1>, <string2>, ... ] }

Here, <string1>, <string2>, ... are the strings that are to be concatenated.

Example

Let us see an example of how to use the $concat operator in MongoDB:

db.products.aggregate([
   {
      $project: {
         itemDescription: {
            $concat: [ "$name", " - ", "$description" ]
         }
      }
   }
])

In the above example, the $concat operator concatenates the name and description fields of the document together, separated by a hyphen. This newly concatenated string is then assigned to the field itemDescription.

Output

The above query will result in a new field in the document named itemDescription with the concatenated string. For example, if the name is "Flowers" and description is "A bouquet of roses", then the output will be like:

{ "_id" : ObjectId("5a0d3abcb189f51623da8cd2"), 
  "name" : "Flowers", 
  "description" : "A bouquet of roses", 
  "itemDescription" : "Flowers - A bouquet of roses" }

Explanation

The $concat operator in MongoDB is used to concatenate strings. It accepts an array of strings and returns a concatenated string. The operator performs concatenation by reading the strings from left to right. The first item in the array is concatenated with the second item, and the result is concatenated with the third item, and so on, until all items have been concatenated.

Use

$concat operator is used in MongoDB aggregation pipelines. It is used to concatenate strings in a document. The operator accepts an array of strings and returns a concatenated string.

Important Points

• The $concat operator in MongoDB is used to concatenate strings.
• The operator performs concatenation by reading the strings from left to right.
• The operator is used in MongoDB aggregation pipelines.

Summary

In this page, we discussed the $concat operator in MongoDB. We covered its syntax, example, output, explanation, use, important points, and summary. The $concat operator is useful in the aggregation pipeline for combining two or more fields into one field.