MongoDB query to convert a string with commas to double

For such conversion, use aggregate(). Let us create a collection with documents −

> db.demo335.insertOne({"Value":"45,67,78.0"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e522a1cf8647eb59e562091")
}
> db.demo335.insertOne({"Value":"17664,76,534.0"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e522a26f8647eb59e562092")
}
> db.demo335.insertOne({"Value":"8899,322,135,875.50"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e522a34f8647eb59e562093")
}
> db.demo335.insertOne({"Value":"1,533.07"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e522ab9f8647eb59e562094")
}

Display all documents from a collection with the help of find() method −

> db.demo335.find();

This will produce the following output −

{ "_id" : ObjectId("5e522a1cf8647eb59e562091"), "Value" : "45,67,78.0" }
{ "_id" : ObjectId("5e522a26f8647eb59e562092"), "Value" : "17664,76,534.0" }
{ "_id" : ObjectId("5e522a34f8647eb59e562093"), "Value" : "8899,322,135,875.50" }
{ "_id" : ObjectId("5e522ab9f8647eb59e562094"), "Value" : "1,533.07" }

Following is the query to convert a string with commas to double −

db.demo335.aggregate([
...    { $project: {
...       data: {
...          $convert: {
...             input: {
...                $reduce: {
...                   input: {
...                      $split: ['$Value', ',']
...                   },
...                   initialValue: '',
...                   in: {
...                      $concat: ['$$value', '$$this']
...                   }
...                }
...             },
...             to: 'double',
...             onError: 0
...          }
...       }
...    }}
... ])

This will produce the following output −

{ "_id" : ObjectId("5e522a1cf8647eb59e562091"), "data" : 456778 }
{ "_id" : ObjectId("5e522a26f8647eb59e562092"), "data" : 1766476534 }
{ "_id" : ObjectId("5e522a34f8647eb59e562093"), "data" : 8899322135875.5 }
{ "_id" : ObjectId("5e522ab9f8647eb59e562094"), "data" : 1533.07 }