"Operator does not exist: integer =?" when using Postgres

Question

I have a simple SQL query called within the QueryRow method provided by go's database/sql package.

import (
  "github.com/codegangsta/martini"
  "github.com/martini-contrib/render"
  "net/http"
  "database/sql"
  "fmt"
  _ "github.com/lib/pq")
)

type User struct {
  Name string
}

func Show(db *sql.DB, params martini.Params) {
  id := params["id"]
  row := db.QueryRow(
    "SELECT name FROM users WHERE id=?", id)
  u := User{}
  err := row.Scan(&u.Name)
  fmt.Println(err)
}

However, I'm getting the error pq: operator does not exist: integer =? It looks like the code doesn't understand that the ? is just a placeholder. How can I fix this?

The reason you get that particular error is that =? would be a valid PostgreSQL operator name. Use id = ?. But as mu says, it's likely also that Go doesn't use ? as a placeholder. — Craig Ringer
– Craig Ringer, Commented Apr 27, 2015 at 4:31

mu is too short · Accepted Answer · 2015-04-27 16:47:30Z

20

PostgreSQL works with numbered placeholders ($1, $2, ...) natively rather than the usual positional question marks. The documentation for the Go interface also uses numbered placeholders in its examples:

rows, err := db.Query("SELECT name FROM users WHERE age = $1", age)

Seems that the Go interface isn't translating the question marks to numbered placeholders the way many interfaces do so the question mark is getting all the way to the database and confusing everything.

You should be able to switch to numbered placeholders instead of question marks:

 row := db.QueryRow(
    "SELECT name FROM users WHERE id = $1", id)

edited Apr 27, 2015 at 16:47

answered Apr 27, 2015 at 4:30

mu is too short

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2 Comments

umezo Over a year ago

got it, thanks. I didn't realize this, as the go docs for database/sql use the question mark. golang.org/pkg/database/sql/#NullString

tomasz Over a year ago

umezo: I'm sure you've already been there, but it's worth reading the documentation for your postgresql driver as well (and not only for the dollar issue): godoc.org/github.com/lib/pq

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