Go实战--go语言操作sqlite数据库(The way to go)

生命不止，继续 go go go !!!

继续与大家分享，go语言的实战，今天介绍的是如何操作sqlite数据库。

何为sqlite3？
SQLite is a self-contained, high-reliability, embedded, full-featured, public-domain, SQL database engine.

最主要的是，sqlite是一款轻型的数据库

官网：
https://www.sqlite.org/

database/sql包
go中有一个database/sql package，我们看看是怎样描述的：
Package sql provides a generic interface around SQL (or SQL-like) databases.

The sql package must be used in conjunction with a database driver

很清晰吧，需要我们自己提供一个database driver。当然，我们可以在github上找到相关的sqlite3的driver，稍后介绍。

下面介绍接个数据相关的操作：

Open

func Open(driverName, dataSourceName string) (*DB, error)

需要提供两个参数，一个driverName，一个数据库的名。

Prepare

func (db *DB) Prepare(query string) (*Stmt, error)

Prepare creates a prepared statement for later queries or executions.
返回的 *Stmt是什么鬼？

Stmt
Stmt is a prepared statement. A Stmt is safe for concurrent use by multiple goroutines.

func (*Stmt) Exec
准备完成后，就要执行了。

func (s *Stmt) Exec(args ...interface{}) (Result, error)

Exec executes a prepared statement with the given arguments and returns a Result summarizing the effect of the statement.
返回的Resault是什么鬼？

Result

type Result interface {
        // LastInsertId returns the integer generated by the database
        // in response to a command. Typically this will be from an
        // "auto increment" column when inserting a new row. Not all
        // databases support this feature, and the syntax of such
        // statements varies.
        LastInsertId() (int64, error)

        // RowsAffected returns the number of rows affected by an
        // update, insert, or delete. Not every database or database
        // driver may support this.
        RowsAffected() (int64, error)
}

Query

func (s *Stmt) Query(args ...interface{}) (*Rows, error)

查询，返回的Rows是什么鬼？

Rows
Rows is the result of a query. Its cursor starts before the first row of the result set.

func (rs *Rows) Next() bool

Next prepares the next result row for reading with the Scan method

func (rs *Rows) Scan(dest ...interface{}) error

Scan copies the columns in the current row into the values pointed at by dest.

介绍少不多了，下面介绍一个sqlite3的Driver：

mattn/go-sqlite3
sqlite3 driver for go that using database/sql
github地址：
https://github.com/mattn/go-sqlite3

执行：

go get -u github.com/mattn/go-sqlite3

下面要开始我们的实战了！！！！

创建数据库，创建表

    //打开数据库，如果不存在，则创建
    db, err := sql.Open("sqlite3", "./test.db")
    checkErr(err)

    //创建表
    sql_table := `
    CREATE TABLE IF NOT EXISTS userinfo(
        uid INTEGER PRIMARY KEY AUTOINCREMENT,
        username VARCHAR(64) NULL,
        departname VARCHAR(64) NULL,
        created DATE NULL
    );
    `

    db.Exec(sql_table)

新建一个数据库叫test.db，并在这个数据库中建一个表，叫做userinfo。
userinfo中包含了四个字段，uid username departname created.
把uid设置为主键，并AUTOINCREMENT，自增。

插入数据

    stmt, err := db.Prepare("INSERT INTO userinfo(username, departname, created) values(?,?,?)")
    checkErr(err)

    res, err := stmt.Exec("wangshubo", "国务院", "2017-04-21")
    checkErr(err)

显示Prepare，然后Exec.

接下来，就不再赘述了，我们需要一个基本的sql知识。

补充：import中_的作用
官方解释：

To import a package solely for its side-effects (initialization), use the blank identifier as explicit package name:

import _ "lib/math"

当导入一个包时，该包下的文件里所有init()函数都会被执行。
然而，有些时候我们并不需要把整个包都导入进来，仅仅是是希望它执行init()函数而已。这个时候就可以使用 import _ 引用该包。

最后献上全部代码：

package main

import (
    "database/sql"
    "fmt"
    "time"

    _ "github.com/mattn/go-sqlite3"
)

func main() {
    //打开数据库，如果不存在，则创建
    db, err := sql.Open("sqlite3", "./foo.db")
    checkErr(err)

    //创建表
    sql_table := `
    CREATE TABLE IF NOT EXISTS userinfo(
        uid INTEGER PRIMARY KEY AUTOINCREMENT,
        username VARCHAR(64) NULL,
        departname VARCHAR(64) NULL,
        created DATE NULL
    );
    `

    db.Exec(sql_table)

    // insert
    stmt, err := db.Prepare("INSERT INTO userinfo(username, departname, created) values(?,?,?)")
    checkErr(err)

    res, err := stmt.Exec("wangshubo", "国务院", "2017-04-21")
    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("wangshubo_new", id)
    checkErr(err)

    affect, err := res.RowsAffected()
    checkErr(err)

    fmt.Println(affect)

    // query
    rows, err := db.Query("SELECT * FROM userinfo")
    checkErr(err)
    var uid int
    var username string
    var department string
    var created time.Time

    for rows.Next() {
        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)
    }
}