Mongodb count() of internal array -

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i have following mongodb collection db.students:

/* 0 */ {     "id" : "0000",     "name" : "john"     "subjects" : [       {         "professor" : "smith",         "day" : "monday"         },       {         "professor" : "smith",         "day" : "tuesday"         }   ] }  /* 1 */ {     "id" : "0001",     "name" : "mike"     "subjects" : [       {         "professor" : "smith",         "day" : "monday"         }     ] }

i want find number of subjects given student. have query:

 db.students.find({'id':'0000'})

that return student document. how find count 'subjects'? doable in simple query?

if query return 1 element : 

db.students.find({'id':'0000'})[0].subjects.length;

for multiple elements in cursor : 

db.students.find({'id':'0000'}).foreach(function(doc) {     print(doc.subjects.length); })

do not forget check existence of subjects either in query or before check .length


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