如何参数化运算符？

Question

I have the following sql statement:

SELECT pk, up FROM mytable WHERE 2 > 1 LIMIT 10

This is just for simplicity, obviously. I am able to parameterize any of the integers:

SELECT pk, up FROM mytable WHERE 2 > $1 LIMIT 10

BUT, when I try to parameterize the operator, eg:

SELECT pk, up FROM mytable WHERE 2 $1 1 LIMIT 10

I get:

pq: syntax error at or near "$1"

Full Code:

package main

import (
    "database/sql"
    _ "github.com/lib/pq"
    "log"
)

func main() {
    log.SetFlags(log.Lshortfile)
    Db, err := sql.Open("postgres", "user=yoitsmeletmein password=supersecretyo host=what.a.host dbname=mydb sslmode=require")
    if err != nil {
        log.Fatal("Cannot connect to db: ", err)
    }
    q := `SELECT pk FROM mytable WHERE 2 $1 1 LIMIT 10`
    params := []interface{}{">"}
    rows, err := Db.Query(q, params...)
    if err != nil {
        log.Println(err)
    } else {
        defer rows.Close()
        for rows.Next() {
            var pk int64
            if err := rows.Scan(&pk); err != nil {
                log.Fatal(err)
            }
            log.Println(pk)
        }
    }

}

Answer 1

Prepared statements allow to parametrize values, nothing else. It wouldn't make sense to parametrize operators to begin with, a statement cannot be prepared without knowing involved operators. And it would be potentially dangerous, opening vectors for SQL injection.

To switch operators, you'll have to concatenate a new query string in your client or use dynamic SQL with a server-side procedural language, the default being plpgsql.