5.2 MySQL

The LAMP stack has been very popular on the internet in recent years, and the M in LAMP stand for MySQL. MySQL is famous because it's open source and easy to use. As such, it became the defacto database in the back-ends of many websites.

MySQL drivers

There are a couple of drivers that support MySQL in Go. Some of them implement the database/sql interface, and others use their own interface standards.

I'll use the first driver in the following examples (I use this one in my personal projects too), and I also recommend that you use it for the following reasons:

  • It's a new database driver and supports more features.
  • Fully supports databse/sql interface standards.
  • Supports keepalive, long connections with thread-safety.

Samples

In the following sections, I'll use the same database table structure for different databases, then create SQL as follows:

CREATE TABLE `userinfo` (
    `uid` INT(10) NOT NULL AUTO_INCREMENT,
    `username` VARCHAR(64) NULL DEFAULT NULL,
    `departname` VARCHAR(64) NULL DEFAULT NULL,
    `created` DATE NULL DEFAULT NULL,
    PRIMARY KEY (`uid`)
);

The following example shows how to operate on a database based on the database/sql interface standards.

package main

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

func main() {
    db, err := sql.Open("mysql", "astaxie:astaxie@/test?charset=utf8")
    checkErr(err)

    // insert
    stmt, err := db.Prepare("INSERT userinfo SET username=?,departname=?,created=?")
    checkErr(err)

    res, err := stmt.Exec("astaxie", "研发部门", "2012-12-09")
    checkErr(err)

    id, err := res.LastInsertId()
    checkErr(err)

    fmt.Println(id)
    // update
    stmt, err = db.Prepare("update userinfo set username=? where uid=?")
    checkErr(err)

    res, err = stmt.Exec("astaxieupdate", id)
    checkErr(err)

    affect, err := res.RowsAffected()
    checkErr(err)

    fmt.Println(affect)

    // query
    rows, err := db.Query("SELECT * FROM userinfo")
    checkErr(err)

    for rows.Next() {
        var uid int
        var username string
        var department string
        var created string
        err = rows.Scan(&uid, &username, &department, &created)
        checkErr(err)
        fmt.Println(uid)
        fmt.Println(username)
        fmt.Println(department)
        fmt.Println(created)
    }

    // delete
    stmt, err = db.Prepare("delete from userinfo where uid=?")
    checkErr(err)

    res, err = stmt.Exec(id)
    checkErr(err)

    affect, err = res.RowsAffected()
    checkErr(err)

    fmt.Println(affect)

    db.Close()

}

func checkErr(err error) {
    if err != nil {
        panic(err)
    }
}

Let me explain a few of the important functions here:

  • sql.Open() opens a registered database driver. The Go-MySQL-Driver registered the mysql driver here. The second argument is the DSN (Data Source Name) that defines information pertaining to the database connection. It supports following formats:

      user@unix(/path/to/socket)/dbname?charset=utf8
  user:password@tcp(localhost:5555)/dbname?charset=utf8
  user:password@/dbname
  user:password@tcp([de:ad:be:ef::ca:fe]:80)/dbname

  • db.Prepare() returns a SQL operation that is going to be executed. It also returns the execution status after executing SQL.

  • db.Query() executes SQL and returns a Rows result.
  • stmt.Exec() executes SQL that has been prepared and stored in Stmt.

Note that we use the format =? to pass arguments. This is necessary for preventing SQL injection attacks.

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