代码：

package main

import (
	_ "github.com/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)
			}
		}
	}
}

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：

Go语言：解决数据库中null值的问题