how to query for multiples rows and parse to json? - sql

Question

I have this code:
func GetAll(c *gin.Context) {
var veiculos model.Veiculo
rows, err := db.Query("SELECT * FROM vei_veiculo")
if err != nil {
fmt.Println("[GetAll] erro ao abrir o query db inteiro")
}
defer rows.Close()
for rows.Next() {
err := rows.Scan(&veiculos)
if err != nil {
fmt.Println("[GetAll] erro ao scanear uma linha'")
}
}
fmt.Println(veiculos)}
My struct name is at model.Veiculo and I want to print it all once. It seems there is an error on scan the query rows. What did I do wrong?

Answer 1

Assuming you are using database/sql, the function signature is func (rs *Rows) Scan(dest ...interface{}) error.
You need to be doing scanning into each member of the struct, something more like:
err := rows.Scan(&veiculos.ID, &veiculos.Name, &veiculos.Description)

Answer 2

To scan each row to its own struct, I recommend an approach like so:
package main
import (
"database/sql"
"fmt"
"log"
_ "github.com/go-sql-driver/mysql"
)
type Person struct {
FirstName string
LastName string
Email string
}
func main() {
db, err := sql.Open("mysql", "dsn...")
if err != nil {
log.Fatalln(err)
}
defer db.Close()
people := []Person{}
rows, err := db.Query("SELECT * FROM people")
if err != nil {
log.Fatalln(err)
}
for rows.Next() {
person := Person{}
if err := rows.Scan(&person.FirstName, &person.LastName, &person.Email); err != nil {
log.Fatalln(err)
}
people = append(people, person)
}
fmt.Printf("%+v\n", people)
}
Alternatively, the library https://github.com/jmoiron/sqlx exists as one of the solutions to marshaling SQL query data to structs. I personally prefer this method, as it behaves more like an Unmarshal function:
package main
import (
"fmt"
"log"
_ "github.com/go-sql-driver/mysql"
"github.com/jmoiron/sqlx"
)
type Person struct {
FirstName string `db:"first_name"`
LastName string `db:"last_name"`
Email string `db:"email"`
}
func main() {
db, err := sqlx.Connect("mysql", "dsn...")
if err != nil {
log.Fatalln(err)
}
people := []Person{}
if err := db.Select(&people, "SELECT * FROM people"); err != nil {
log.Fataln(err)
}
fmt.Printf("%+v\n", people)
}
Following either of these approaches allows you to easily use the json.Marshal
method with the people variable, and viola!
Good luck!