C#数据库操作：增加、删除、更新、读取
首先，数据库基础的创建使用参考我的另一个：https://blog.csdn.net/qq_17242837/article/details/105376817
可以参考网站开发用的MySQL命令
// Command Action，命令集
ALTER Alter a database or table
BACKUP Back up a table
\c Cancel input
CREATE Create a database
DELETE Delete a row from a table
DESCRIBE Describe a table’s columns
DROP Delete a database or table
EXIT (CTRL-C) Exit
GRANT Change user privileges
HELP (\h, \?) Display help
INSERT Insert data
LOCK Lock table(s)
QUIT (\q) Same as EXIT
RENAME Rename a table
SHOW List details about an object
SOURCE Execute a fle
STATUS (\s) Display the current status
TRUNCATE Empty a table
UNLOCK Unlock table(s)
UPDATE Update an existing record
USE Use a database其中常见数据库命令
// 创建表格
CREATE TABLE category(id int IDENTITY(1, 1) PRIMARY KEY not null,cname char(50))
// 在表格中添加数据
INSERT INTO category(id, cname) VALUES(@id, '@name')
// 表格中更新数据
UPDATE category SET cname = @cname WHERE id = @id;
// 表格中删除数据
DELETE FROM category WHERE id = '@id'
// 读取数据
select * from category where id = '@id'以下是我适用声明的数据库，可以直接使用
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
// 使用SQL数据库操作
using System.Data;
using System.Data.Sql;
using System.Data.SqlClient;
using System.Data.OleDb; // 保存accdb时使用
namespace PublicFunctionLib
{
class MySQL
{
// 需要现在“视图”》“服务器资源管理器”中添加本地数据库，对应数据库属性中“连接字符串”复制给connect string
string connectString = @"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\21994\Documents\test.mdf;Integrated Security=True;Connect Timeout=30";
SqlConnection sqlCnt; // 数据库连接
SqlCommand command; // 数据库命令控制
public MySQL()
{
try
{
sqlCnt = new SqlConnection(connectString);
sqlCnt.Open();
// 以下可以直接使用这个函数：SqlCommand command = sqlCnt.CreateCommand();
command = new SqlCommand();
command.Connection = sqlCnt; // 绑定SqlConnection对象
command.CommandType = CommandType.Text;
//// 执行SQL命令（也可以这样重复使用）
//command = new SqlCommand("CREATE TABLE category(id int IDENTITY(1, 1) PRIMARY KEY not null,cname char(50))", sqlCnt);
//command.ExecuteNonQuery();
//// 设定控制命令，并执行。在new的写入命令也可以，但目前这个如果已经有这个表格再添加会停止这
//command.CommandText = "CREATE TABLE 表格2(text int IDENTITY(1, 1) PRIMARY KEY not null,cname char(50))";
//command.ExecuteNonQuery();
Console.WriteLine("数据库初始化成功");
}
catch { }
}
///
/// 输入数据库控制命令，并执行
///
///
///
/// 对category执行写入数据，加上我以后用于添加用户
///
///
///
public void write(int id, string name = "")
{
// 需要先执行更改为可以写入
commend("set identity_insert category on");
//INSERT INTO users(id, name) VALUES(1, 'name')
string commandText = "INSERT INTO category(id, cname) VALUES(@id, '" + name + "')";
SqlParameter[] ar_Para = new SqlParameter[] {
new SqlParameter("@id", SqlDbType.Int),
new SqlParameter("@cname", SqlDbType.NChar)
};
ar_Para[0].Value = id;
ar_Para[1].Value = name;
command.Parameters.Clear(); // 需要先清空，不然会报错提示已声明
command.Parameters.AddRange(ar_Para);
command.CommandText = commandText;
//command.Parameters.Add("@id", SqlDbType.Int); // 添加参数及其类型
//command.Parameters["@id"].Value = id; // 设定更改后的参数值
//command.Parameters[1].Value = name;
// Use AddWithValue to assign Demographics.
// SQL Server will implicitly convert strings into XML.
//command.Parameters.AddWithValue("@name", name);
try
{
Int32 rowsAffected = command.ExecuteNonQuery();
Console.WriteLine("RowsAffected: {0}", rowsAffected);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
///
/// 删除对应id的一行数据
///
///
public void delete(int id)
{
//DELETE FROM classics WHERE title='Little Dorrit';
commend("DELETE FROM category WHERE id = '" + id + "'");
}
// 更新第几个id数据为什么
public void update(int id, string name)
{
string commandText = "UPDATE category SET cname = @cname "
+ "WHERE id = @id;";
SqlParameter[] ar_Para = new SqlParameter[] {
new SqlParameter("@id", SqlDbType.Int),
new SqlParameter("@cname", SqlDbType.NChar)
};
ar_Para[0].Value = id;
ar_Para[1].Value = name;
command.Parameters.AddRange(ar_Para);
command.CommandText = commandText;
//command.Parameters.Add("@id", SqlDbType.Int); // 添加参数及其类型
//command.Parameters["@id"].Value = id; // 设定更改后的参数值
//command.Parameters[1].Value = name;
// Use AddWithValue to assign Demographics.
// SQL Server will implicitly convert strings into XML.
//command.Parameters.AddWithValue("@name", name);
try
{
Int32 rowsAffected = command.ExecuteNonQuery();
Console.WriteLine("RowsAffected: {0}", rowsAffected);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
// 没毛病，下载是可以正常读取数据出来
public void reader(string queryString = "", string connectionString = "")
{
if (queryString.Length > 0)
command.CommandText = "select * from category where id = \'" + queryString + "\'";
else
command.CommandText = "select * from category";
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
// 读取数据库单行长度
for(int i = 0; i < reader.VisibleFieldCount; i++)
Console.WriteLine(String.Format("{0}", reader[i]));
// 数据库不为空
//if (reader.HasRows)
//{
// Console.WriteLine(String.Format("{0}", reader[1]));
//}
}
reader.Close();
}
///
/// 数据库命令测试
///
public void commandTest()
{
string str = "";
while (str != "exit")
{
Console.WriteLine("请输入你的控制命令");
str = Console.ReadLine();
if (str == "read")
{
string cmd = Console.ReadLine();
reader(cmd);
}
else if (str == "write")
{
write(Convert.ToInt32(Console.ReadLine()), Console.ReadLine());
}
else if (str == "delete")
delete( Convert.ToInt32(Console.ReadLine()) );
else if (str == "update")
update(Convert.ToInt32(Console.ReadLine()), Console.ReadLine());
else
commend(str);
}
}
// 析构函数，不用添加public
~MySQL()
{
try
{
command.Dispose();
sqlCnt.Close();
}
catch { }
}
}
}