Question

What would be the Mongodb equivalent of the 2 following SQL queries?

SELECT A.Lname FROM Assistant A INNER JOIN Manager Ma ON A.RefNum = Ma.RefNum

GROUP BY A.Lname HAVING COUNT(DISTINCT Ma.Manager) > 1;

SELECT G.Cname, R.Snum FROM Game G

INNER JOIN Role R ON G.Cnum = R.Cnum

WHERE G.level>200;

Answer 1

Dear Student,

Here are the MongoDB equivalents of the 2 SQL statements,

db..group({

   "key":{
         "A.Lname ": true
   },
   "initial": {

   },
   "reduce": function( obj , prev ){


   },
   "finalize": function( prev ){

   },
   "cond": {
        "$where": "this.CT A.Lname FROM Assistant A INNER JOIN Manager Ma ON A.RefNum  == this. Ma.RefNum  "
   }

});

db.GameG INNER JOIN Role R ON G.Cnum = R.Cnum .find({
        "G.level":{ "$gt" : 200 }
},{
        "G.Cname": 1,
        "R.Snum": 1
}
);