Checking if a value exists in sqlite db with Go - sql

Question

I'm writing code to manage users in a sqlite database with Go.
I'm trying to check if a username is taken, but my code is ugly.
My table looks like:
id INTEGER PRIMARY KEY AUTOINCREMENT,
username TEXT UNIQUE,
password TEXT
And I check if a username is taken with:
func UserExists(db * sql.DB, username string) bool {
sqlStmt := `SELECT username FROM userinfo WHERE username = ?`
count := 0
rows, err := db.Query(sqlStmt, username)
Check(err)
for rows.Next() { // Can I just check if rows is non-zero somehow?
count++
}
return len(rows) != 0
}
Is there a better query I could use that would tell me if the username value exists in the table in a more staight forward way? Or is there a nicer way to check if rows is non-zero?

Answer 1

Use QueryRow to query at most one row. If the query doesn't return any row, it returns sql.ErrNoRows.
func UserExists(db * sql.DB, username string) bool {
sqlStmt := `SELECT username FROM userinfo WHERE username = ?`
err := db.QueryRow(sqlStmt, username).Scan(&username)
if err != nil {
if err != sql.ErrNoRows {
// a real error happened! you should change your function return
// to "(bool, error)" and return "false, err" here
log.Print(err)
}
return false
}
return true
}

Answer 2

I know this is a bit old, but I don't see any clean answers here. Notice below the if rows.Next() statement which will return a boolean if there are any rows or not:
package main
import (
"database/sql"
_ "github.com/mattn/go-sqlite3"
"log"
)
func main() {
exists, _ := SelectDBRowExists(`SELECT * FROM GEO_VELOCITY_EVENTS WHERE USERNAME='bob'`)
log.Println(exists)
}
func SelectDBRowExists(query string) (bool, error) {
DbConn, err := sql.Open("sqlite3", "/path/to/your/sql.sqlite3")
if err != nil {
return false, err
}
defer DbConn.Close()
err = DbConn.Ping()
if err != nil {
return false, err
}
rows, err := DbConn.Query(query)
if rows.Next() {
return true, nil
} else {
return false, nil
}
defer rows.Close()
return false, nil
}

Answer 3

as long as you are only concerned about the existence of one single information in the Database. I found that this method is quite simpler and efficient.
func emailExists(email string) bool {
row := db.QueryRow("select user_email from users where user_email= ?", email)
checkErr(err)
temp := ""
row.Scan(&temp)
if temp != "" {
return true
}
return false
}
if u noticed am only getting a single row.
the result of my Query gets scanned in a temp Variable.
then I check whether the temp Variable is empty or not.
if it is not empty, true is returned.

Answer 4

i think we can use above function to check that condition is already exist at database.
if helper.UserExists(db, username) {
return username, errors.New("data already exist")
}
because that function returned bool that means if that function is called return will return by default is true.
i hope this usefull.