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

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)

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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)

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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)

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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)

}

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Query

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

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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

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

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

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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

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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)

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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)

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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"

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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)

}

}

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