Examples

Many use cases are covered by the tests of Go-MySQL-Driver. You might find what you are looking for there.

Prepared Statements

Assume an empty table with the following layout:

+--------------+---------+------+-----+---------+-------+
| Field        | Type    | Null | Key | Default | Extra |
+--------------+---------+------+-----+---------+-------+
| number       | int(11) | NO   | PRI | NULL    |       |
| squareNumber | int(11) | NO   |     | NULL    |       |
+--------------+---------+------+-----+---------+-------+

In this example we prepare two statements - one for inserting tuples (rows) and one to query.

package main

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

func main() {
	db, err := sql.Open("mysql", "user:password@/database")
	if err != nil {
		panic(err.Error())
	}
	defer db.Close()

	// Prepare statement for inserting data
	stmtIns, err := db.Prepare("INSERT INTO squareNum VALUES( ?, ? )") // ? = placeholder
	if err != nil {
		panic(err.Error())
	}
	defer stmtIns.Close() // Close the statement when we leave main() / the program terminates

	// Prepare statement for reading data
	stmtOut, err := db.Prepare("SELECT squareNumber FROM squarenum WHERE number = ?")
	if err != nil {
		panic(err.Error())
	}
	defer stmtOut.Close()

	// Insert square numbers for 0-24 in the database
	for i := 0; i < 25; i++ {
		_, err = stmtIns.Exec(i, (i * i)) // Insert tuples (i, i^2)
		if err != nil {
			panic(err.Error())
		}
	}

	var squareNum int // we "scan" the result in here

	// Query the square-number of 13
	err = stmtOut.QueryRow(13).Scan(&squareNum) // WHERE number = 13
	if err != nil {
		panic(err.Error())
	}
	fmt.Printf("The square number of 13 is: %d", squareNum)

	// Query another number.. 1 maybe?
	err = stmtOut.QueryRow(1).Scan(&squareNum) // WHERE number = 1
	if err != nil {
		panic(err.Error())
	}
	fmt.Printf("The square number of 1 is: %d", squareNum)
}

Ignoring NULL values

Note: This might cause problems in Go 1.0 since the conversion from integer types to []byte is missing. The Issue is fixed in Go 1.1+

Maybe you already encountered this error: sql: Scan error on column index 1: unsupported driver -> Scan pair: <nil> -> *string

Normally you would use sql.NullString in such a case. But sometimes you don't care if the value is NULL, you just want to treat it as an empty string.

You can do this with a small workaround, which takes advantage of the fact, that a nil-[]byte gets converted to an empty string.

Instead of using *string as a rows.Scan(...) destination, you simple use *[]byte (or *sql.RawBytes), which can take the nil value:

[...]
var col1, col2 []byte

for rows.Next() {
	// Scan the value to []byte
	err = rows.Scan(&col1, &col2)

	// Use the string value
	fmt.Println(string(col1), string(col2))
}

RawBytes

package main

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

func main() {
	// Open database connection
	db, err := sql.Open("mysql", "user:password@@tcp(127.0.0.1:3306)/dbname?charset=utf8")
	if err != nil {
		panic(err.Error())
	}
	defer db.Close()

	// Execute the query
	rows, err := db.Query("SELECT * FROM table")
	if err != nil {
		panic(err.Error())
	}

	// Get column names
	columns, err := rows.Columns()
	if err != nil {
		panic(err.Error())
	}

	// Make a slice for the values
	values := make([]sql.RawBytes, len(columns))

	// rows.Scan wants '[]interface{}' as an argument, so we must copy the
	// references into such a slice
	// See http://code.google.com/p/go-wiki/wiki/InterfaceSlice for details
	scanArgs := make([]interface{}, len(values))
	for i := range values {
		scanArgs[i] = &values[i]
	}

	// Fetch rows
	for rows.Next() {
		// get RawBytes from data
		err = rows.Scan(scanArgs...)
		if err != nil {
			panic(err.Error())
		}

		// Now do something with the data.
		// Here we just print each column as a string.
		var value string
		for i, col := range values {
			// Here we can check if the value is nil (NULL value)
			if col == nil {
				value = "NULL"
			} else {
				value = string(col)
			}
			fmt.Println(columns[i], ": ", value)
		}
		fmt.Println("-----------------------------------")
	}
}

Feel free to contribute your own examples!