golang 数据库空字段问题

超、凢脫俗 2022-06-02 10:15 274阅读 0赞

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)
    			}
    		}
    	}
    }

数据库查询截图：

![SouthEast][]

运行结果截图：

![SouthEast 1][]

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][Go_null] #

[SouthEast]: /images/20220602/218269b0d7ba4d98bf39269e18f5216d.png
[SouthEast 1]: /images/20220602/1958921eb3b64388ab07fa6a5080bcc4.png
[Go_null]: http://blog.csdn.net/qq_15437667/article/details/78780945