module5-examples.md

Module 5 Examples

Array Query Operators

1. Find all the crew members where all the skills are either 'tehchnical' or 'sales'

db.crew.find({ skills: {$all: ["technical", "sales"]}})

2. Find all the crew members that have exactly 2 skills

db.crew.find({ skills: { $size: 2} })

3. Find all the crew members where the skill object matches multiple conditions

db.crew.find({skills: {$elemMatch: {name: "flying", lvl: {$gt: 7}}}})

Array Projection Operators

1. Show first 2 elements from an array when performing queries

db.crew.find({}, {skills: {$slice: 2})

2. Show the first element that matches the array querying

db.crew.find({skills: "management"}, {"skills.$":1})

3. Only display the array elements that match a list of given conditions

db.crew.find({}, {skills: { $elemMatch: {lvl: {$gt: 7}} } })

Demo Queryies

1. Flights containing at least a German crew member

db.flights.find({"crew.nationality": "Germany"},{crew: 1}).pretty()

db.flights.find({"crew.nationality": "Germany"},{"crew.$": 1}).pretty()

2. Flights that do not have a crew (size is 0)

db.flights.find({crew: []}, {crew:1}).pretty()

db.flights.find({crew: {$size: 0}},{crew: 1}).pretty()

3. Flights that do not have a captain

db.flights.find({"crew.position": {$ne: "Captain"}}, {"crew.position": 1}).pretty()

4. Flights where the captain has little hours of sleep (7)

db.flights.find({crew: {$elemMatch: {position: "Captain", hoursSlept: {$gt: 6}}}}, {crew: 1}).pretty()

db.flights.find({crew: {$elemMatch: {position: "Captain", hoursSlept: {$gt: 6}}}}, {"crew.$": 1}).pretty()

5. Display only the captain in the crew array when querying the flight documents

db.flights.find({}, {crew: {$elemMatch: {position: "Captain"}}}).pretty()