Create, Read, Update, Delete
This exercise will help you practice your ability to query and mondify data in MongoDB.
Start a shell connecting to:
And answer the following questions about the students.scores collection.
- How many scores are there?
- What are the different
kind’s of scores? - How many of each kind of score does each student have?
- How many students got at least a 90 on their exam?
- How many students got less than a 60 on their quiz?
- Create a copy of all the scores in another collection to use later, then update all the
students who got less than a 60 on any kind of score with a new field,
needsHelp:true - Find the student with the lowest number which has the lowest overall quiz score and then delete all the scores for that student - he was expelled.
- A new student transfered into your school, add them to the scores collection. (Make up values for the the new students score's on each kind of score.)
Switch over to the fruits collection and inspect the apples collection.
Find all the apples which have color=green and taste=sweet-tart tags.
MongoDB documents can have properties which are arrays. This is a powerful feature, but you need to practice caution when quering to make sure your results are valid.
Switch over to the stuff database and inspect the elems collection.
If you want to find the elems with “a” = { “b”:1,”c”:4 }
you might try this query db.elems.find( { "a.b" : 1, "a.c" : 4 } ).
Do the results look correct?
How do I group and perform operations on query results in MongoDB? The Aggregation Framework.
Back to the students.scores namespace.
What is and which student got the highest exam score and the lowest quiz score?