Question

Is it possible to express the following SQL query in mongodb:

SELECT * FROM table AS t WHERE t.field1 > t.filed2;

edit:
To summarize:.

1. using a third field storing “field1 – field2” is almost perfect, but requires a little extra maintenance.
2. $where will load and eval in JavaScript and won’t use any indexes. No good for large data.
3. map/reduce has the same problem and will go trough all records even if we need only one

Answer 1

You can do this using $where:

db.coll.find( { $where: "this.field1 > this.field2" } );

But:

Javascript executes more slowly than
the native operators, but it is very flexible

If performance is an issue better to go with way suggested by @yi_H.