问题 I have MongoDB collection called changes which contains following data { "date" : ISODate("2014-06-09T00:00:00.000Z"), "field" : "ip", "from" : "157.11.209.123", "to" : "107.21.109.254" } { "date" : ISODate("2014-05-15T00:00:00.000Z"), "field" : "ip", "from" : "107.21.109.254", "to" : "157.11.209.123" } { "date" : ISODate("2014-06-09T00:00:00.000Z"), "field" : "registration", "from" : "Old service", "to" : "Some new service" } Then I want to make typical SQL query that counts occurrences and