goweb连接数据库操作

连接数据库

增加

package main

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

func main() {
	//打开链接
	db, err := sql.Open("mysql", "root:123456@tcp(localhost:3306)/first")
	db.Ping()
	defer func() {
		if db != nil {
			db.Close()
		}
	}()
	if err != nil {
		fmt.Println("数据库连接失败")
		return
	}
	//预处理sql
	stmt, err := db.Prepare("insert into people values(default,?,?)")
	defer func() {
		if stmt != nil {
			stmt.Close()
		}
	}()
	if err != nil {
		fmt.Println("预处理失败")
		return
	}
	result, err := stmt.Exec("张三", "大海")
	if err != nil {
		fmt.Println("sql失败")
		return
	}
	//获取结果
	count, err := result.RowsAffected()
	if err != nil {
		fmt.Println("获取结果失败")
		return
	}
	if count > 0 {
		fmt.Println("新增成功")
	} else {
		fmt.Println("新增失败")
	}

	//可能需要获取新增时主键的值
	id, _ := result.LastInsertId()
	fmt.Println(id)
}

修改

修改和新增类似，只是不需要获取LastInsertId()和Sql语句是修改语句

在Golang中要求：如果修改前和修改后的值相同，RowAffected()返回0，即修改失败

package main

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

func main() {
	db, _ := sql.Open("mysql", "root:123456@tcp(localhost:3306)/first")
	defer func() {
		if db != nil {
			db.Close()
		}
	}()
	stmt, _ := db.Prepare("update people set name = ? where id = ?")
	defer func() {
		if stmt != nil {
			stmt.Close()
		}
	}()
	result, _ := stmt.Exec("李四", 2)
	count, _ := result.RowsAffected()
	if count > 0 {
		fmt.Println("修改成功")
	} else {
		fmt.Println("修改失败")
	}
}

删除

删除和修改，新增结构一样

在Go语言中要求如果要删除的数据不存在，RowsAffected()返回0

package main

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

func main() {
	db, _ := sql.Open("mysql", "root:123456@tcp(localhost:3306)/first")
	defer func() {
		if db != nil {
			db.Close()
		}
	}()
	stmt, err := db.Prepare("delete from people where id = 3")
	if err != nil {
		fmt.Println("预处理出错")
	}
	defer func() {
		if stmt != nil {
			stmt.Close()
		}
	}()
	result, err := stmt.Exec()
	if err != nil {
		fmt.Println("执行失败")
		return
	}
	count, _ := result.RowsAffected()
	if count > 0 {
		fmt.Println("删除成功")
	} else {
		fmt.Println("删除失败")
	}
}

数据查询

Golang中执行查询与增删改中stmt的执行方法有区别，由于需要把查询的结果取出来，所以还需要进行取值处理

执行查询Sql时，stmt调用的是Query()方法

package main

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

func main() {
	db, err := sql.Open("mysql", "root:123456@tcp(localhost:3306)/first")
	if err != nil {
		fmt.Println("连接失败")
		return
	}
	defer func() {
		if db != nil {
			db.Close()
		}
	}()
	stmt, err := db.Prepare("select * from people")
	if err != nil {
		fmt.Println("预处理失败")
		return
	}
	defer func() {
		if stmt != nil {
			stmt.Close()
		}
	}()
	rows, err := stmt.Query()
	if err != nil {
		fmt.Println("获取结果失败")
		return
	}
	defer func() {
		if rows != nil {
			rows.Close()
		}
	}()
	var id int
	var name, adderss string
	for rows.Next() {
		rows.Scan(&id, &name, &adderss)
		fmt.Println(id, name, adderss)
	}
}