golang mysql驱动程序无法替换参数

Question

OS Mojave, MySQL v8.0.15, go 1.12.3 darwin/amd64

import (
    "database/sql"

    // import mysql driver anonymously (just run the init)
    _ "github.com/go-sql-driver/mysql"
)

...

_, err = db.db.Exec("USE ?", "test")
if err != nil {
    return errors.Wrapf(err, "error selecting database %s", opt.Database)
}

_, err = db.db.Prepare("SELECT value FROM ? WHERE key = ?")
if err != nil {
    return errors.Wrap(err, "error generating SELECT statement")
}

The error I get is error selecting database test: Error 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?' at line 1

I get the same error (about syntax around '?') for any parameter replacement I attempt to do. I've checked the manual as well as tutorials and examples I've found online and can't quite tell what I'm doing wrong.

If I replace the '?'s with values (strings) then everything works fine.

Answer 1

Question marks ? in prepared statements are for values, not table, database or column names.

Use fmt.Sprintf to fill in the database structure related values.

Example:

_, err := db.db.Prepare(fmt.Sprintf("SELECT value FROM %s WHERE key = ?", table))