golang mysql nil

golang mysql nil"/>

golang mysql nil

代码：

package main

import (

_ "github/go-sql-driver/mysql"

"fmt"

"database/sql"

)

func main() {

d13()

fmt.Println("--------------------------")

d14()

}

func d13(){

var err error

connect := "f:f@tcp(192.168.1.0:3306)/lr1"

db, err := sql.Open("mysql", connect)

if err != nil{

fmt.Println("connect mysql failed, address = " + connect, err)

} else{

sqlContent := "select real_nm, sex, birth, ext from member where tenant=? and mem_id=?"

rows, err := db.Query(sqlContent, "ST", "2017")

if err != nil{

fmt.Println(err)

} else{

for rows.Next() {

var nm string

var sex string

var birth string

var ext string

err := rows.Scan(&nm, &sex,&birth, &ext) // birth字段在数据库中是空字段

if err != nil{

fmt.Println("d11 error. ", err)

}

fmt.Println(nm)

fmt.Println(sex)

fmt.Println(birth)

fmt.Println(ext)

}

}

}

}

func d14(){

var err error

connect := "f:f@tcp(192.168.1.0:3306)/lr1"

db, err := sql.Open("mysql", connect)

if err != nil{

fmt.Println("connect mysql failed, address = " + connect, err)

} else{

sqlContent := "select real_nm, sex, birth, ext from member where tenant=? and mem_id=?"

rows, err := db.Query(sqlContent, "ST", "2017")

if err != nil{

fmt.Println(err)

} else{

for rows.Next() {

nm := sql.NullString{String:"", Valid:false}

sex := sql.NullString{String:"", Valid:false}

birth := sql.NullString{String:"", Valid:false}

ext := sql.NullString{String:"", Valid:false}

err := rows.Scan(&nm, &sex,&birth, &ext) // birth字段在数据库中是空字段

if err != nil{

fmt.Println("d12 error. ", err)

}

fmt.Println(nm.String)

fmt.Println(sex.String)

fmt.Println(birth.String)

fmt.Println(ext.String)

}

}

}

}

数据库查询截图：

运行结果截图：

因为数据库的birth字段为空，所以它在给golang的string对象birth赋值时，出错了(golang的 string不能等于nil)所以后续的数据库的ext就没有再赋值给golang的ext对象了， 而是返回error对象

参考路径：