[Quang Ma] Week 2 - SQL to GORM Assignment

cmd/app/main.go

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+package main
+
+import (
+	"assignment_1_gorm"
+	"fmt"
+
+	"gorm.io/driver/mysql"
+	"gorm.io/gorm"
+)
+
+// main connects to database and does the exercises in sol-1.sql and sol-2.sql
+func main() {
+	// Connect to the MySQL database
+	dsn := "quangmx:2511@tcp(127.0.0.1:3306)/engineerpro?charset=utf8mb4&parseTime=True&loc=Local"
+	db, err := gorm.Open(mysql.Open(dsn), &gorm.Config{})
+	if err != nil {
+		panic("Failed to connect to database")
+	}
+
+	initDatabase(db)
+
+	// Những cặp student-professor có dạy học nhau và số lớp mà họ có liên quan
+	related_stud_prof(db)
+
+	// Những course (distinct) mà 1 professor cụ thể đang dạy
+	teaching_courses(db, 1)
+
+	// // TODO: Implement this
+	// // Những course (distinct) mà 1 student cụ thể đang học
+	// studying_courses(db, 1)
+
+	// // TODO: Implement this
+	// // điểm số là A, B, C, D, E, F tương đương với 10, 8, 6, 4, 2, 0
+	// convert_grade(db)
+
+	// // TODO: Implement this
+	// // điểm số trung bình của 1 học sinh cụ thể (quy ra lại theo chữ cái, và xếp loại học lực (weak nếu avg < 5, average nếu >=5 < 8, good nếu >=8 )
+	// stud_avg_grade(db, 1)
+
+	// // TODO: Implement this
+	// // điểm số trung bình của các class (quy ra lại theo chữ cái)
+	// class_avg_grade(db)
+
+	// // TODO: Implement this
+	// // điểm số trung bình của các course (quy ra lại theo chữ cái)
+	// course_avg_grade(db)
+
+}
+
+// initDatabase creates tables and adds records
+func initDatabase(db *gorm.DB) {
+	// Delete tables if existed
+	db.Migrator().DropTable(&assignment_1_gorm.Professor{})
+	db.Migrator().DropTable(&assignment_1_gorm.Student{})
+	db.Migrator().DropTable(&assignment_1_gorm.Course{})
+	db.Migrator().DropTable(&assignment_1_gorm.Class{})
+	db.Migrator().DropTable(&assignment_1_gorm.Enroll{})
+	fmt.Println("Tables deleted successfully...")
+
+	// Create tables
+	db.Migrator().CreateTable(&assignment_1_gorm.Professor{})
+	db.Migrator().CreateTable(&assignment_1_gorm.Student{})
+	db.Migrator().CreateTable(&assignment_1_gorm.Course{})
+	db.Migrator().CreateTable(&assignment_1_gorm.Class{})
+	db.Migrator().CreateTable(&assignment_1_gorm.Enroll{})
+	fmt.Println("Tables created successfully...")
+
+	// Create records
+	var result *gorm.DB
+	professors := []assignment_1_gorm.Professor{
+		{FirstName: "Albus", LastName: "Dumbledore"},
+		{FirstName: "Severus", LastName: "Snape"},
+		{FirstName: "Alastor", LastName: "Moody"},
+	}
+	result = db.Create(&professors)
+	if result.Error != nil {
+		panic(result.Error)
+	}
+
+	students := []assignment_1_gorm.Student{
+		{FirstName: "Harry", LastName: "Potter", Street: "Privet Drive 1", City: "London", Zip: "100000"},
+		{FirstName: "Hermione", LastName: "Granger", Street: "Privet Drive 2", City: "London", Zip: "200000"},
+		{FirstName: "Ron", LastName: "Weasly", Street: "Privet Drive 3", City: "London", Zip: "300000"},
+	}
+	result = db.Create(&students)
+	if result.Error != nil {
+		panic(result.Error)
+	}
+
+	courses := []assignment_1_gorm.Course{
+		{Name: "Physical Education"},
+		{Name: "Quidditch"},
+		{Name: "Defence Against the Dark Arts"},
+		{Name: "Potion"},
+	}
+	result = db.Create(&courses)
+	if result.Error != nil {
+		panic(result.Error)
+	}
+
+	classes := []assignment_1_gorm.Class{
+		{Name: "PE1", ProfessorID: 1, CourseID: 1, RoomLoc: "001", RoomCap: "100"},
+		{Name: "QD1", ProfessorID: 2, CourseID: 2, RoomLoc: "002", RoomCap: "200"},
+		{Name: "DA1", ProfessorID: 3, CourseID: 3, RoomLoc: "003", RoomCap: "300"},
+		{Name: "DA2", ProfessorID: 3, CourseID: 3, RoomLoc: "004", RoomCap: "400"},
+		{Name: "PT1", ProfessorID: 3, CourseID: 4, RoomLoc: "005", RoomCap: "500"},
+	}
+	result = db.Create(&classes)
+	if result.Error != nil {
+		panic(result.Error)
+	}
+
+	enrolls := []assignment_1_gorm.Enroll{
+		{StudentID: 1, ClassID: 2, Grade: "B"},
+		{StudentID: 2, ClassID: 1, Grade: "A"},
+		{StudentID: 2, ClassID: 2, Grade: "A"},
+		{StudentID: 2, ClassID: 3, Grade: "A"},
+		{StudentID: 3, ClassID: 1, Grade: "C"},
+		{StudentID: 3, ClassID: 3, Grade: "D"},
+		{StudentID: 1, ClassID: 4, Grade: "D"},
+		{StudentID: 2, ClassID: 4, Grade: "D"},
+		{StudentID: 3, ClassID: 4, Grade: "D"},
+	}
+	result = db.Create(&enrolls)
+	if result.Error != nil {
+		panic(result.Error)
+	}
+
+	fmt.Println("Records created successfully...")
+}
+
+// Những cặp student-professor có dạy học nhau và số lớp mà họ có liên quan
+func related_stud_prof(db *gorm.DB) {
+	type Record struct {
+		StudentID   int `gorm:"column:stud_id"`
+		ProfessorID int `gorm:"column:prof_id"`
+		Count       int `gorm:"column:num_class"`
+	}
+	var records []Record
+	query := `
+select
+    distinct stud_id,
+    prof_id,
+    count(*) as num_class
+from
+    Class
+    join Enroll using (class_id)
+group by
+    stud_id,
+    prof_id
+order by
+    stud_id;`
+	db.Raw(query).Scan(&records)
+
+	// Print to console
+	fmt.Println("\nNhững cặp student-professor có dạy học nhau và số lớp mà họ có liên quan")
+	for _, record := range records {
+		fmt.Printf("%+v\n", record)
+	}
+}
+
+// Những course (distinct) mà 1 professor cụ thể đang dạy
+func teaching_courses(db *gorm.DB, prof_id int) {
+	type Record struct {
+		CourseID int `gorm:"column:course_id"`
+	}
+	var records []Record
+	query := `
+select
+    distinct course_id
+from
+    Class
+where
+    prof_id = ?;`
+	db.Raw(query, prof_id).Scan(&records)
+
+	// Print to console
+	fmt.Printf("\nNhững course (distinct) mà professor %d đang dạy\n", prof_id)
+	for _, record := range records {
+		fmt.Printf("%+v\n", record)
+	}
+}

go.mod

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+module assignment_1_gorm
+
+go 1.20
+
+require gorm.io/gorm v1.25.1
+
+require github.com/go-sql-driver/mysql v1.7.0 // indirect
+
+require (
+	github.com/jinzhu/inflection v1.0.0 // indirect
+	github.com/jinzhu/now v1.1.5 // indirect
+	gorm.io/driver/mysql v1.5.1
+)

go.sum

@@ -0,0 +1,10 @@
+github.com/go-sql-driver/mysql v1.7.0 h1:ueSltNNllEqE3qcWBTD0iQd3IpL/6U+mJxLkazJ7YPc=
+github.com/go-sql-driver/mysql v1.7.0/go.mod h1:OXbVy3sEdcQ2Doequ6Z5BW6fXNQTmx+9S1MCJN5yJMI=
+github.com/jinzhu/inflection v1.0.0 h1:K317FqzuhWc8YvSVlFMCCUb36O/S9MCKRDI7QkRKD/E=
+github.com/jinzhu/inflection v1.0.0/go.mod h1:h+uFLlag+Qp1Va5pdKtLDYj+kHp5pxUVkryuEj+Srlc=
+github.com/jinzhu/now v1.1.5 h1:/o9tlHleP7gOFmsnYNz3RGnqzefHA47wQpKrrdTIwXQ=
+github.com/jinzhu/now v1.1.5/go.mod h1:d3SSVoowX0Lcu0IBviAWJpolVfI5UJVZZ7cO71lE/z8=
+gorm.io/driver/mysql v1.5.1 h1:WUEH5VF9obL/lTtzjmML/5e6VfFR/788coz2uaVCAZw=
+gorm.io/driver/mysql v1.5.1/go.mod h1:Jo3Xu7mMhCyj8dlrb3WoCaRd1FhsVh+yMXb1jUInf5o=
+gorm.io/gorm v1.25.1 h1:nsSALe5Pr+cM3V1qwwQ7rOkw+6UeLrX5O4v3llhHa64=
+gorm.io/gorm v1.25.1/go.mod h1:L4uxeKpfBml98NYqVqwAdmV1a2nBtAec/cf3fpucW/k=

model.go

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+package assignment_1_gorm
+
+// CREATE TABLE Professor (
+//
+//	prof_id INT AUTO_INCREMENT,
+//	prof_fname VARCHAR(50),
+//	prof_lname VARCHAR(50),
+//	PRIMARY KEY (prof_id)
+//
+// );
+type Professor struct {
+	ID        uint32 `gorm:"column:prof_id;type:int(32);primary_key;auto_increment"`
+	FirstName string `gorm:"column:prof_fname;type:varchar(50)"`
+	LastName  string `gorm:"column:prof_lname;type:varchar(50)"`
+}
+
+func (Professor) TableName() string {
+	return "Professor"
+}
+
+// CREATE TABLE Student (
+//
+//	stud_id INT AUTO_INCREMENT,
+//	stud_fname VARCHAR(50),
+//	stud_lname VARCHAR(50),
+//	stud_street VARCHAR(255),
+//	stud_city VARCHAR(50),
+//	stud_zip VARCHAR(10),
+//	PRIMARY KEY (stud_id)
+//
+// );
+type Student struct {
+	ID        uint32 `gorm:"column:stud_id;type:int(32);primary_key;auto_increment"`
+	FirstName string `gorm:"column:stud_fname;type:varchar(50)"`
+	LastName  string `gorm:"column:stud_lname;type:varchar(50)"`
+	Street    string `gorm:"column:stud_street;type:varchar(255)"`
+	City      string `gorm:"column:stud_city;type:varchar(50)"`
+	Zip       string `gorm:"column:stud_zip;type:varchar(10)"`
+}
+
+func (Student) TableName() string {
+	return "Student"
+}
+
+// CREATE TABLE Course (
+//
+//	course_id INT AUTO_INCREMENT,
+//	course_name VARCHAR(255),
+//	PRIMARY KEY (course_id)
+//
+// );
+type Course struct {
+	ID   uint32 `gorm:"column:course_id;type:int(32);primary_key;auto_increment"`
+	Name string `gorm:"column:course_name;type:varchar(255)"`
+}
+
+func (Course) TableName() string {
+	return "Course"
+}
+
+// -- Class and Room are joined into 1 table Class
+// CREATE TABLE Class (
+//
+//	class_id INT AUTO_INCREMENT,
+//	class_name VARCHAR(255),
+//	prof_id INT,
+//	course_id INT,
+//	room_loc VARCHAR(50),
+//	room_cap VARCHAR(50),
+//	PRIMARY KEY (class_id),
+//	FOREIGN KEY (prof_id) REFERENCES Professor(prof_id),
+//	FOREIGN KEY (course_id) REFERENCES Course(course_id)
+//
+// );
+type Class struct {
+	ID          uint32 `gorm:"column:class_id;type:int(32);primary_key;auto_increment"`
+	Name        string `gorm:"column:class_name;type:varchar(255)"`
+	ProfessorID uint32 `gorm:"column:prof_id;type:int(32)"`
+	CourseID    uint32 `gorm:"column:course_id;type:int(32)"`
+	RoomLoc     string `gorm:"column:room_loc;type:varchar(50)"`
+	RoomCap     string `gorm:"column:room_cap;type:varchar(50)"`
+
+	Professor Professor `gorm:"foreign_key:prof_id;references:prof_id"`
+	Course    Course    `gorm:"foreign_key:course_id;references:course_id"`
+}
+
+func (Class) TableName() string {
+	return "Class"
+}
+
+// CREATE TABLE Enroll (
+//
+//	stud_id INT,
+//	class_id INT,
+//	grade VARCHAR(3),
+//	PRIMARY KEY (stud_id, class_id),
+//	FOREIGN KEY (stud_id) REFERENCES Student(stud_id),
+//	FOREIGN KEY (class_id) REFERENCES Class(class_id)
+//
+// );
+type Enroll struct {
+	StudentID int    `gorm:"column:stud_id;type:int(32);primary_key"`
+	ClassID   int    `gorm:"column:class_id;type:int(32);primary_key"`
+	Grade     string `gorm:"column:grade;type:varchar(3)"`
+
+	Student Student `gorm:"foreign_key:stud_id;references:stud_id"`
+	Class   Class   `gorm:"foreign_key:class_id;references:class_id"`
+}
+
+func (Enroll) TableName() string {
+	return "Enroll"
+}

sol-1.sql

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+-- Solution for Capital Gain/Loss
+select
+    stock_name,
+    sum(
+        case
+            when operation = "Buy" then - price
+            else price
+        end
+    ) as capital_gain_loss
+from
+    Stocks
+group by
+    stock_name;
+
+-- Solution for Count Salary Categories
+select
+    "Low Salary" as "category",
+    count(*) as "accounts_count"
+from
+    Accounts
+where
+    Accounts.income < 20000
+union
+select
+    "Average Salary" as "category",
+    count(*) as "accounts_count"
+from
+    Accounts
+where
+    income >= 20000
+    and income <= 50000
+union
+select
+    "High Salary" as "category",
+    count(*) as "accounts_count"
+from
+    Accounts
+where
+    income > 50000;