How to use MySQL

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How to use 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.

supports database/sql, written in pure Go.
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.

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