Conditional operator if-condition
Example:
[{"_id" : ObjectId("6024b764abea6cc5c99ceefd"),"name" : "George","grade" : 5.0,"school" : "MathHighSchool"}{"_id" : ObjectId("6024b764abea6cc5c99ceefe"),"name" : "John","grade" : 4.0,"school" : "MathHighSchool"}{"_id" : ObjectId("6024b764abea6cc5c99ceeff"),"name" : "Paul","grade" : 3.0,"school" : "MathHighSchool"}{"_id" : ObjectId("6024b764abea6cc5c99cef00"),"name" : "Ringo","grade" : 5.0,"school" : "MathHighSchool"}{"_id" : ObjectId("6024b764abea6cc5c99cef01"),"name" : "Johnny","grade" : 2.0,"school" : "MathHighSchool"}{"_id" : ObjectId("6024b764abea6cc5c99cef02"),"name" : "Joshua","grade" : 7.0,"school" : "MathHighSchool"}]
Approach
Query: Query to identify which student is pass(>=3) or fail(<3).
db.people.aggregate([{$match:{"school":"MathHighSchool"}},{$project:{"school":1,"div": {$cond:{ if:{ $gte:["$grade",3]},then:"pass",else:"fail"}}}}]);
Output:
[{"_id" : ObjectId("6024b764abea6cc5c99ceefd"),"school" : "MathHighSchool","div" : "pass"}{"_id" : ObjectId("6024b764abea6cc5c99ceefe"),"school" : "MathHighSchool","div" : "pass"}{"_id" : ObjectId("6024b764abea6cc5c99ceeff"),"school" : "MathHighSchool","div" : "pass"}{"_id" : ObjectId("6024b764abea6cc5c99cef00"),"school" : "MathHighSchool","div" : "pass"}{"_id" : ObjectId("6024b764abea6cc5c99cef01"),"school" : "MathHighSchool","div" : "fail"}{"_id" : ObjectId("6024b764abea6cc5c99cef02"),"school" : "MathHighSchool","div" : "pass"}]
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