golang mysql exec占位符“？”未扩展

Question

I feel like I must be totally missing the point. I try to run something along the lines of the example below, but the ? is not expanded into the argument passed in.

import (
    "database/sql"
    _ "github.com/go-sql-driver/mysql"
)

db, err := sql.Open(...)
if err != nil { ... }
_, err = db.Query("SELECT * FROM foo WHERE bar=?", bar)

Also, who's concern is expanding it? it show's up in the doc of database/sql but other conversations hinted it may be the concern of the driver.

What am I missing? Any pointer in the right direction is greatly appreciated.

Answer 1

You're (probably) not telling it to use the mysql driver;

db, err := sql.Open("mysql", connString)

Here is some of my sample code:

var query = "INSERT IGNORE INTO blah (`col1`, `col2`, `col3`) VALUES (?, ?, ?)"

r, err := db.Query(query, some_data_1, some_data_2, some_data_3)

// Failure when trying to store data
if err != nil {
    msg := fmt.Sprintf("fail : %s", err.Error())
    fmt.Println(msg)

    return err
}

r.Close() // Always do this or you will leak connections

I create the MySQL pool (yes, it's a pool NOT a connection) with:

import (
    // mysql driver
    _ "github.com/go-sql-driver/mysql"

    "database/sql"
    "fmt"
)

connString := fmt.Sprintf("%s:%s@(%s:%d)/%s?timeout=30s",
    user,
    password,
    host,
    port,
    database,
)

db, err := sql.Open("mysql", connString)

if err != nil {
    return nil, err
}

err = db.Ping() // test the pool connection(s)

if err != nil {
    return nil, err
}

return db, nil // No error, return the pool connections

I also highly suggest you print out any errors in the database connection process and query process. It could be that you are using the driver, but you lack permissions, the database is down, etc.