Go Lang, Postgres: cannot get oid after Scan

Question

I have 2 columns if table accounts:

oid and balance

By the next code I try to extract oid then balance:

// variable `id` comes from an another part

sqlstr := `SELECT * ` +
    `FROM accounts ` +
    `WHERE oid=` + id + `;`

q, err := db.Query(sqlstr)

if err != nil {
    fmt.Println("Error: GetAccount \n", err)
    return Account{}, err
}
defer q.Close()


var _id string
var bal float64

q.Next()
q.Scan(&_id)
fmt.Println("_id ", _id)


q.Next()
q.Scan(&bal)
fmt.Println("bal ", bal)

After the first q.Next() I expected to extract oid and after the second to extract balance.

But every time after the first q.Next() and after the second I only get balance.

I tried to change sqlstr to the next:

sqlstr := `SELECT oid, balance ` +
    `FROM accounts ` +
    `WHERE oid=` + id + `;`

But I still cannot extract oid.

ssemilla · Accepted Answer · 2018-11-12 17:28:16Z

1

Try this q.Scan(&_id, &bal), func (*Row) Scan has this signature:

func (r *Row) Scan(dest ...interface{}) error

It expects the the pointers to the values where it will store the queried data.

If you are only querying for a single row, there is func (*DB) QueryRow(). Then your code will simplify to

row := db.QueryRow(sqlstr)
err := row.Scan(&_id, &bal)
// err will be sql.ErrNoRows if no rows have been selected

edited Nov 12, 2018 at 17:28

answered Nov 12, 2018 at 17:16

ssemilla

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8 Comments

meteor Over a year ago

It says: sql: expected 1 destination arguments in Scan, not 2

ssemilla Over a year ago

What exact PG library are you using? Is it this one: github.com/lib/pq? How are you opening your database connection?

ssemilla Over a year ago

Are you opening your DB connection like this: db, err := sql.Open("postgres", connStr)?

meteor Over a year ago

I use github.com/lib/pq as DB driver, but to connect DB I use github.com/xo/dburl

meteor Over a year ago

So the solution is to use oid, balance instead of * in sql query string, to use db.QueryRow() instead of db.Query(), and to use row.Scan(&_id, &bal) according to oid, balance in sql query string.

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