db.test1.insertOne(
   {
      "StudentId" :1,
      "StudentName" : "Joseph Connor"
   }
)

db.test1.find()

show dbs
db.dropDatabase()
show dbs

// remove tinker
use tinker
db.test1.find()
doc = {
      "StudentId" :1,
      "StudentName" : "Joseph Connor"
}
doc
if (db.test1.find(doc).count() == 0) { db.test1.insertOne(doc) }
db.test1.find()
if (db.test1.find(doc).count() == 0) { db.test1.insertOne(doc) }
db.test1.find()

doc2 = {
	"StudentId" :1
}

db.test1.find(doc2)
db.test1.find()
// remove tinker
show dbs
db.dropDatabase()
show dbs
// create index
db.test1.createIndex( 
	{ "StudentId": 1 }, // 1st argument: fields in the index; 1: true
	{ unique: true } )  // 2nd argument: property of the index
doc = {
      "StudentId" :1,
      "StudentName" : "Joseph Connor"
}
doc
db.test1.insertOne(doc)
db.test1.insertOne(doc)

db.test1.insertMany([
   {   "StudentId" :2,
      "GPA": 3.72
   },
   {   "StudentId" :3,
      "GPA": 1.69
   },
   {
      "BCAssetId": "78c22fc6-5dec-11ec-bf63-0242ac130002",
      "BCAssetType": "BCAssetTypeMetadata",
      "BCAssetName": "BCAssetTypeMetadata: MBSEModel",
      "ForBCAssetType": "MBSEModel",
      "Version": {
         "Version": "1.0",
         "Subversion": null,
         "StartTime": "2019-01-13T07:23:13+06:00"
      }
   }
])
db.test1.find()

mongorestore --archive="toyu-db.gz" --gzip --nsFrom='toyu.*' --nsTo='toyu.*'

db.student.find()
// db.collection.find(query, projection, options
db.student.find(
	{}, // query: compare to the WHERE clause in SQL
    { "_id": 0 }  // projection; 0: false; compare to the SELECT clause in the SELECT statement.
)


db.student.find(
	{}, // query
    { "_id": 0,  "studentId": 1, "major": 1
	}  // projection; 0: false
)

db.student.find(
	{}, // query
    { "_id": 0,  "stuId": 1, "major": 1
	}  // projection; 0: false
)

db.student.find(
	{"major": "CSCI" }, // query
    { "_id": 0,  "stuId": 1, "major": 1
	}  // projection; 0: false
)

db.student.find(
	{"major": "CSCI", "minor":"CINF" }, // query
    { "_id": 0,  "stuId": 1, "major": 1, "minor":1
	}  // projection; 0: false
)

db.student.find(
	{"majo": "CSCI", "minor":"CINF"}, // query
    { "_id": 0,  "stuId": 1, "major": 1, "minor":1
	}  // projection; 0: false
)

// 
Returns:	A cursor to the documents that match the query criteria. When the find() method "returns documents," the method is actually returning a cursor to the documents.
result = db.student.find({},
   { "fname": 1, "lname":1, "_id": 0 }  
).toArray()

result.forEach((x,i) => console.log('student #' + String(i) + ': ' + x["fname"] + ' ' + x["lname"]))

result.forEach((x,i) => console.log('student #' + String(i+1) + ': ' + x["fname"] + ' ' + x["lname"]))

// [5] Show the names and credits (ach) of students majoring in 'CSCI' and having 40 or more credits.
// SQL: ..> WHERE major = 'CSCI' AND ach >= 40;

db.student.find(
   { "major": "CSCI", "ach" : {$gte: 40} },
   { "fname": 1, "lname":1, "major": 1, "ach":1, "_id": 0 }  
)

db.student.find(  // return an empty cursor.
   { "major": "CSCI", "ach" : {gte: 40} },
   { "fname": 1, "lname":1, "major": 1, "ach":1, "_id": 0 }  
)

// [6] Show the first name and last name of students with a first name starting with a L or B, case insensitive.
//       SELECT s.fname, s.lname
		 FROM student AS s
		 WHere s.fname REGEXP '^[lb]';
db.student.find(
	// $regex: need to match the regular expression.
	//  regex is embedded by two /'s.
	//  actual regex: ^[lb]
	// ^ matches the beginning position.
	// [lb]: character class: matches 1 char
   { "fname": { $regex: /^[lb]/, $options: "i" } },
   { "fname": 1, "lname":1, "_id": 0 }  
)

// Show the names and credits (ach) of students majoring in 'CSCI' and having 40 or more credits.
db.student.find(
   { "$and": [ { "major": "CSCI"}, { "ach": {"$gte": 40}} ] },
   { "fname": 1, "lname":1, "ach":1, "_id": 0 }  
)

// Show the names and credits (ach) of students [1] majoring in 'CSCI' and having 40 or more credits, or [2] majoring in 'CINF'
db.student.find(
	{ "$or": [{ "$and": [ { "major": "CSCI"}, { "ach": {"$gte": 40}} ] },
			   { "major": "CINF"}]}
   ,
   { "fname": 1, "lname":1, "major": 1, "ach":1, "_id": 0 }  
)
// SELECT DISTINCT s.fname, s.lname, s.major, s.ach
   FROM Student AS s
   WHERE (s.major = 'CSCI' AND s.ach >= 40) OR s.major = 'CINF';

db.faculty.find(
	{  "deptCode": {"$in": ["CINF", "ITEC"] }},
	{	"faculty": {"concat": ["$fname", " ", "$lname"]}, 
        "deptCode": 1, "rank": 1, "_id": 0,  }	
)

db.student.aggregate([
{$lookup:
    {
      from: "enroll",
      let: {joinValue: '$stuId'},
      pipeline: [
           { $match:
                 { $expr:
                    { $and:
                       [
                         { $eq: [ "$stuId",  "$$joinValue" ] },
                         { $eq: [ "$classId", 10000 ] }
                       ]
                    }
                 }
            }    
        ],
        as: "enrollment"     }},
  { $match: {"enrollment":  { $ne: [] }}},  
  { $project: { "fname": 1, "lname": 1, "_id": 0}} 
])