# 5.2 MySQL

The framework call LAMP is very popular on the internet in recent years, and the M is the MySQL. MySQL is famous by its open source, easy to use, so it becomes the database in the back-end of many websites.

## MySQL drivers

There are couple of drivers that support MySQL in Go, some of them implemented `database/sql` interface, and some of them use their only interface standards.

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

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

- It's a new database driver and supports more features.
- Fully support `databse/sql` interface standards.
- Support keepalive, long connection with thread-safe.

## Samples

In following sections, I'll use same database table structure for different databases, the 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 database based on `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 few important functions:

- `sql.Open()` opens a registered database driver, here the Go-MySQL-Driver registered mysql driver. The second argument is DSN(Data Source Name) that defines information of 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 SQL operation that is going  to execute, also returns execute status after executed SQL.
- `db.Query()` executes SQL and returns Rows result.
- `stmt.Exec()` executes SQL that is prepared in Stmt.

Note that we use format `=?` to pass arguments, it is for preventing SQL injection.

## Links

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