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 has become the de-facto 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 supports database/sql, written in pure Go.
• https://github.com/ziutek/mymysql supports database/sql and 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.
• It fully supports database/sql interface standards.
• Supports keep-alive, 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)
	    }
	    
	    rows.Close()
	
	    // 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
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