GO API: Database Connection

GO API: Database Connection

client_db.go

 package db  
   
 import (  
      "database/sql"  
      _ "github.com/lib/pq"  
      . "test.com/goapi/app/utils"  
      "sync"  
      "log"  
 )  
   
 var (  
      db    *sql.DB  
      ConnOnce sync.Once  
 )  
   
 // create database connection  
 func GetDBConnection() *sql.DB {  
      var err error  
      ConnOnce.Do(func() {  
           db, err = sql.Open("postgres", "postgresql://"+COCKROACHDB_USERNAME_ENV+"@"+COCKROACHDB_HOST_ENV+":"+COCKROACHDB_PORT_ENV+  
                "/"+COCKROACHDB_DB_ENV+"?"+"sslmode=disable")  
      })  
      if err != nil {  
           log.Fatal("error connecting to the database: ", err)  
      }  
      return db  
 }  
   
 func ExecuteQuery(query string, args string) *sql.Rows{  
      db := GetDBConnection()  
      if args == "" {  
           rows, err := db.Query(query)  
           if err != nil {  
                log.Println("Error in executing query: ", err)  
           }  
           return rows  
      } else {  
           rows, err := db.Query(query, args)  
           if err != nil {  
                log.Println("Error in executing query: ", err)  
           }  
           return rows  
      }  
 }  
   
 func ExecuteCreateQuery(query string, args []interface{}) {  
      db := GetDBConnection()  
      _, err := db.Query(query, args...)  
      if err != nil {  
           log.Println("Error in executing query: ", err)  
      }  
 }  

student_db.go

 package db  
   
 import (  
      . "test.com/goapi/app/model"  
      "database/sql"  
      "log"  
 )  
   
 func parseRow(rows *sql.Rows) []Student {  
      var students []Student  
      for rows.Next() {  
           var (  
                rollNumber int  
                name    string  
                batch   string  
                branch   string  
           )  
           if err := rows.Scan(&rollNumber, &name, &batch, &branch); err != nil {  
                log.Println("error in parsing ", err)  
           }  
           student := Student{  
                RollNumber: rollNumber,  
                Name: name,  
                Batch: batch,  
                Branch: branch,  
           }  
           students = append(students, student)  
      }  
      return students  
 }  
   
 func GetStudentsDB() []Student{  
      query := "SELECT * FROM student_tlb"  
      rows := ExecuteQuery(query, "")  
      students := parseRow(rows)  
      return students   
 }  
   
 func GetStudentDB(rollNumber string) Student{  
      query := "SELECT * FROM student_tlb WHERE roll_number = $1"  
      rows := ExecuteQuery(query, rollNumber)  
      students := parseRow(rows)  
      return students[0]   
 }  
   
 func CreateStudentDB(student Student) {  
      args := make([]interface{}, 4)  
      args[0] = student.RollNumber  
      args[1] = student.Name  
      args[2] = student.Batch  
      args[3] = student.Branch  
      query := "INSERT INTO student_tlb (roll_number, name, batch, branch) VALUES($1, $2, $3, $4)"  
      ExecuteCreateQuery(query, args)  
 }  
   
 func UpdateStudentDB(student Student) {  
      args := make([]interface{}, 4)  
      args[0] = student.Name  
      args[1] = student.Batch  
      args[2] = student.Branch  
      args[3] = student.RollNumber  
      query := "UPDATE student_tlb SET (name, batch, branch) = ($1, $2, $3) WHERE roll_number = $4"  
      ExecuteCreateQuery(query, args)  
 }  
   
 func DeleteStudentDB(rollNumber string) {  
      query := "DELETE FROM student_tlb WHERE roll_number = $1"  
      ExecuteQuery(query, rollNumber)  
 }  

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