MongoDB $gt/$lt operators with prices stored as strings

Question

I\'m trying to query my database for prices greater than/less than a user specified number. In my database, prices are stored like so:

{price: \"300.00\"}
         


        

Answer 1

$gt is an operator that can work on any type:

db.so.drop();
db.so.insert( { name: "Derick" } );
db.so.insert( { name: "Jayz" } );
db.so.find( { name: { $gt: "Fred" } } );

Returns:

{ "_id" : ObjectId("51ffbe6c16473d7b84172d58"), "name" : "Jayz" }

If you want to compare against a number with $gt or $lt, then the value in your document also needs to be a number. Types in MongoDB are strict and do not auto-convert like they f.e. would do in PHP. In order to solve your issue, make sure you store the prices as numbers (floats or ints):

db.so.drop();
db.so.insert( { price: 50.40 } );
db.so.insert( { price: 29.99 } );
db.so.find( { price: { $gt: 30 } } );

Returns:

{ "_id" : ObjectId("51ffbf2016473d7b84172d5b"), "price" : 50.4 }