05.2.md

# 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.

- [https://github.com/go-sql-driver/mysql](https://github.com/go-sql-driver/mysql) supports `database/sql`, written in pure Go.
- [https://github.com/ziutek/mymysql](https://github.com/ziutek/mymysql) supports `database/sql` and user defined interfaces, written in pure Go.
- [https://github.com/Philio/GoMySQL](https://github.com/Philio/GoMySQL) only supports user defined interfaces, written in pure Go.

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 `database/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,
	    `department` 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=?,department=?,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.

## Links

- [Directory](preface.md)
- Previous section: [database/sql interface](05.1.md)
- Next section: [SQLite](05.3.md)