Go sqlx库

sqlx is a library which provides a set of extensions on go's standard database/sql library.

sqlx support some db:  mysql, postgresql, oracle, sqlite ...

https://github.com/jmoiron/sqlx

示例代码：

该库目前只对查询进行了深度封装，对于更新和插入封装较少。

新建表

package main

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

    "github.com/jmoiron/sqlx"
)

var schema = `Create table person2(
first_name varchar(20),
last_name varchar(20),
email varchar(20));
`

var schema2 = `Create table place(
country varchar(20),
city varchar(20) NULL,
telcode int(20));
`

type Person struct {
    FirstName string `db:"first_name"`
    LastName string `db:"last_name"`
    Email string
}

type Place struct {
    Country string
    city sql.NullString
    TelCode int
}

func main() {
    dsn := "root:123456@tcp(172.16.65.200:3306)/golang"
    db, err := sqlx.Connect("mysql", dsn)
    if err != nil {
        panic(err)
    }

    result, err := db.Exec(schema2)
    if err != nil {
        panic(err)
    }
    _, err = result.RowsAffected()
    if err != nil {
        panic(err)
    }

}

单行查询使用 sqlx.Get()，多行查询使用 sqlx.Select()

package main

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

type User struct {
    Id   int    `db:"id"`
    Name string `db:"name"`
    Age  int    `db:"age"`
}

// 单行查询，如果查询到多个结果，只返回第一行，查询不到结果就ErrNoRows错误。
func QueryRow(db *sqlx.DB) {
    var user User
    err := db.Get(&user, "select id, name, age from user where id=?", 1)
    if err == sql.ErrNoRows {
        log.Printf("not found data of the id:%d", 1)
    }

    if err != nil {
        panic(err)
    }

    fmt.Printf("user: %#v
", user)
}

// 多行查询, 查询不到任何记录也不会报错。
func Query(db *sqlx.DB) {
    var users []*User
    err := db.Select(&users, "select id, name, age from user")
    if err != nil {
        panic(err)
    }
    if err == sql.ErrNoRows {
        log.Printf("not found data")
        return
    }

    for _, user := range users {
        fmt.Println(user.Id, user.Name)
    }
}

func main() {
    dsn := "root:123456@tcp(172.16.65.200:3306)/golang"
    db, err := sqlx.Connect("mysql", dsn)
    if err != nil {
        panic(err)
    }

    err = db.Ping()
    if err != nil {
        panic(err)
    }

    fmt.Printf("connect to db success
")

    QueryRow(db)

    Query(db)
}

更新和插入使用sqlx.Exec()

package main

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

func Update(db *sqlx.DB) {
    name := "Miles"
    age := 88
    id := 3

    result, err := db.Exec("update user set name=?, age=? where id=?", name, age, id)
    if err != nil {
        panic(err)
    }

    // RowsAffected returns the number of rows affected by an
    // update, insert, or delete.
    rowsAffected, err := result.RowsAffected()
    if err != nil {
        panic(err)
    }

    fmt.Printf("update id:%d, affect rows:%d
", id, rowsAffected)

}


func Insert(db *sqlx.DB) {
    name := "Lucy"
    age := 18

    result, err := db.Exec("insert into user(name, age) values (?,?)", name, age)
    if err != nil {
        panic(err)
    }

    id, err := result.LastInsertId()
    if err != nil {
        panic(err)
    }

    affected, err := result.RowsAffected()
    if err != nil {
        panic(err)
    }

    fmt.Printf("last insert id:%d affect rows:%d
", id, affected)
}

func main() {
    dsn := "root:123456@tcp(172.16.65.200:3306)/golang"
    db, err := sqlx.Connect("mysql", dsn)
    if err != nil {
        panic(err)
    }

    err = db.Ping()
    if err != nil {
        panic(err)
    }
    fmt.Println("connect to db success!!!")
    Update(db)
    Insert(db)
}

预处理，直接使用原生的sql.db，没有进行过任何封装

package main

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

type User2 struct {
    Id int `db:"id"`
    Name string `db:"name"`
    Age int `db:"age"`
}


// 预处理是为了提高查询性能；
// 实现的原理是先将查询语句发送给Mysql数据库做预解析；
// 然后再将需要查询的条件数据发送给Mysql数据库进行执行；
// 这种原理类似于GO语言和Python语言执行效率的对比；
// Go语言是需要先编译的，Python是一边执行一边编译。
func PrepareQuery(db *sqlx.DB, id int) {
    stmt, err := db.Prepare("select id, name, age from user where id>?")
    if err != nil {
        panic(err)
    }

    rows, err := stmt.Query(id)
    if err != nil {
        panic(err)
    }

    defer stmt.Close()
    defer rows.Close()

    for rows.Next(){
        var user User2
        err := rows.Scan(&user.Id, &user.Name, &user.Age)
        if err != nil {
            panic(err)
        }
        fmt.Printf("user: %#v
", user)
    }
}

func main() {

    dsn := "root:123456@tcp(172.16.65.200:3306)/golang"
    db, err := sqlx.Connect("mysql", dsn)
    if err != nil {
        panic(err)
    }

    defer db.Close()

    PrepareQuery(db, 1)

}

原则性操作

package main

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


func Transaction(db *sqlx.DB) {

    // 开启事务
    tx, err := db.Begin()

    if err != nil {
        panic(err)
    }

    result, err := tx.Exec("insert into user(name, age)values(?,?)", "Jack", 98)
    if err != nil {
        // 失败回滚
        tx.Rollback()
        panic(err)
    }

    fmt.Println("result", result)

    exec, err := tx.Exec("update user set name=?, age=? where id=?", "Jack", 98, 1)
    if err != nil {
        // 失败回滚
        tx.Rollback()
        panic(err)
    }
    fmt.Println("exec", exec)

    // 提交事务
    err = tx.Commit()

    if err != nil {
        // 失败回滚
        tx.Rollback()
        panic(err)
    }
}

func main() {

    dsn := "root:123456@tcp(172.16.65.200:3306)/golang"
    db, err := sqlx.Connect("mysql", dsn)
    if err != nil {
        panic(err)
    }

    err = db.Ping()
    if err != nil {
        panic(err)
    }

    Transaction(db)
}

Named

    // Named queries can use structs, so if you have an existing struct (i.e. person := &Person{}) that you have populated, you can pass it in as &person
    tx.NamedExec("INSERT INTO person (first_name, last_name, email) VALUES (:first_name, :last_name, :email)", &Person{"Jane", "Citizen", "jane.citzen@example.com"})
    tx.Commit()

更多用法

package main

import (
    "database/sql"
    "fmt"
    "log"
    
    _ "github.com/lib/pq"
    "github.com/jmoiron/sqlx"
)

var schema = `
CREATE TABLE person (
    first_name text,
    last_name text,
    email text
);

CREATE TABLE place (
    country text,
    city text NULL,
    telcode integer
)`

type Person struct {
    FirstName string `db:"first_name"`
    LastName  string `db:"last_name"`
    Email     string
}

type Place struct {
    Country string
    City    sql.NullString
    TelCode int
}

func main() {
    // this Pings the database trying to connect, panics on error
    // use sqlx.Open() for sql.Open() semantics
    db, err := sqlx.Connect("postgres", "user=foo dbname=bar sslmode=disable")
    if err != nil {
        log.Fatalln(err)
    }

    // exec the schema or fail; multi-statement Exec behavior varies between
    // database drivers;  pq will exec them all, sqlite3 won't, ymmv
    db.MustExec(schema)
    
    tx := db.MustBegin()
    tx.MustExec("INSERT INTO person (first_name, last_name, email) VALUES ($1, $2, $3)", "Jason", "Moiron", "jmoiron@jmoiron.net")
    tx.MustExec("INSERT INTO person (first_name, last_name, email) VALUES ($1, $2, $3)", "John", "Doe", "johndoeDNE@gmail.net")
    tx.MustExec("INSERT INTO place (country, city, telcode) VALUES ($1, $2, $3)", "United States", "New York", "1")
    tx.MustExec("INSERT INTO place (country, telcode) VALUES ($1, $2)", "Hong Kong", "852")
    tx.MustExec("INSERT INTO place (country, telcode) VALUES ($1, $2)", "Singapore", "65")
    // Named queries can use structs, so if you have an existing struct (i.e. person := &Person{}) that you have populated, you can pass it in as &person
    tx.NamedExec("INSERT INTO person (first_name, last_name, email) VALUES (:first_name, :last_name, :email)", &Person{"Jane", "Citizen", "jane.citzen@example.com"})
    tx.Commit()

    // Query the database, storing results in a []Person (wrapped in []interface{})
    people := []Person{}
    db.Select(&people, "SELECT * FROM person ORDER BY first_name ASC")
    jason, john := people[0], people[1]

    fmt.Printf("%#v
%#v", jason, john)
    // Person{FirstName:"Jason", LastName:"Moiron", Email:"jmoiron@jmoiron.net"}
    // Person{FirstName:"John", LastName:"Doe", Email:"johndoeDNE@gmail.net"}

    // You can also get a single result, a la QueryRow
    jason = Person{}
    err = db.Get(&jason, "SELECT * FROM person WHERE first_name=$1", "Jason")
    fmt.Printf("%#v
", jason)
    // Person{FirstName:"Jason", LastName:"Moiron", Email:"jmoiron@jmoiron.net"}

    // if you have null fields and use SELECT *, you must use sql.Null* in your struct
    places := []Place{}
    err = db.Select(&places, "SELECT * FROM place ORDER BY telcode ASC")
    if err != nil {
        fmt.Println(err)
        return
    }
    usa, singsing, honkers := places[0], places[1], places[2]
    
    fmt.Printf("%#v
%#v
%#v
", usa, singsing, honkers)
    // Place{Country:"United States", City:sql.NullString{String:"New York", Valid:true}, TelCode:1}
    // Place{Country:"Singapore", City:sql.NullString{String:"", Valid:false}, TelCode:65}
    // Place{Country:"Hong Kong", City:sql.NullString{String:"", Valid:false}, TelCode:852}

    // Loop through rows using only one struct
    place := Place{}
    rows, err := db.Queryx("SELECT * FROM place")
    for rows.Next() {
        err := rows.StructScan(&place)
        if err != nil {
            log.Fatalln(err)
        } 
        fmt.Printf("%#v
", place)
    }
    // Place{Country:"United States", City:sql.NullString{String:"New York", Valid:true}, TelCode:1}
    // Place{Country:"Hong Kong", City:sql.NullString{String:"", Valid:false}, TelCode:852}
    // Place{Country:"Singapore", City:sql.NullString{String:"", Valid:false}, TelCode:65}

    // Named queries, using `:name` as the bindvar.  Automatic bindvar support
    // which takes into account the dbtype based on the driverName on sqlx.Open/Connect
    _, err = db.NamedExec(`INSERT INTO person (first_name,last_name,email) VALUES (:first,:last,:email)`, 
        map[string]interface{}{
            "first": "Bin",
            "last": "Smuth",
            "email": "bensmith@allblacks.nz",
    })

    // Selects Mr. Smith from the database
    rows, err = db.NamedQuery(`SELECT * FROM person WHERE first_name=:fn`, map[string]interface{}{"fn": "Bin"})

    // Named queries can also use structs.  Their bind names follow the same rules
    // as the name -> db mapping, so struct fields are lowercased and the `db` tag
    // is taken into consideration.
    rows, err = db.NamedQuery(`SELECT * FROM person WHERE first_name=:first_name`, jason)
}