數據庫的基本使用（C#語言）

目錄

• insert
• select 的使用
• delete
• update 更新
• Like模糊查詢
• Order 排序
• GETDATA()
• 聚合函數：MAX，MIN，AVG，SUM，COUNT
  • Max
  • COUNT
• ADO.Net 平臺的使用
  • 在C#中使用的格式
  • insert 在 C# 的使用
  • delete 的使用

數據庫的基本使用
@

insert

格式： insert into 表名() values()
其中，values 是帶s

**格式： i**nsert into T1(name,age) values('aaa',30)
T1是表名；
name，age 是T1表中的鍵名，則'aaa',30是分別對應的值  
== >values中的順序要和表名後的順序一致。

select 的使用

格式： select Name,Id from T1
Name, Id 是表中的鍵名，多個鍵名之間使用逗號分開
T1 是表格

delete

"delete from Table_Student where Name ='aaa' "; 
   
delete from T_Student where Name='yzk'   

從 T_Student表中刪除Name字段等於yzk的數據

delete from T_Student  刪除全部數據

delete from T_Student where Age>100 or Name='yzk' 或者

delete from T_Student where Age>100 and Height>150  而且

update 更新

update T_Student set Age=Age+1

update T_Student set Age=Age+1,AiHao='吃飯'

update T_Student set AiHao='散步' where Age>100

select * from T_Student where Age<30

---

Like模糊查詢

select * from T_Student where Name like 'y%'    這個是查詢以y開頭的數據

select * from T_Student where Name like 'y%k'   這個是查詢以y開頭,  k爲結尾的數據


select * from T_Student where Name like '%a%'   查詢含有名字中含有a 的數據

Order 排序

按照一個字段排序 select * from T_Student order by Age 默認是升序排列

select * from T_Student order by Age, Height

若是Age同樣，則再按照Height排序

下面是降序排列，降序Descending

select * from T_Student order by Age Desc

下面是若是Age同樣，則再按照Height排序

select * from T_Student order by Age, Height DEsc

下面的語句是一個總體

select * from T_Student where Name like 'y%' 
order by Age

where要在order by以前

GETDATA()

GETDATA()，sql 內置的函數
用來獲取當前時間
其中，下面的as是在查詢結果顯示的時候，起別名

select Name as selectname, GETDATE() from Table_Student

聚合函數：MAX，MIN，AVG，SUM，COUNT

Max

查詢Height、Age的最大值
select Max(Height) as maxid, Age as myAge   from Table_Student

COUNT

下面是查詢在Age > 100 中全部的行數
select COUTN(*) from Table_Student where Age >100

ADO.Net 平臺的使用

簡介：.Net中用來向數據庫提交執行SQL語句的一堆類。

在C#中使用的格式

// SqlConnection 繼承的父類 SqlConnection 實如今對自動回收接口的繼承
            // public abstract class DbConnection : Component, IDbConnection, IDisposable
            /* SqlConnection 實例化創建新的鏈接
             *  Data Source 表示 IP,若是是本機通訊的話，只須要寫 .  就能夠了
             *  Initial Catalog 對應的數據庫中將要操做的表格
             *  User ID 表示數據庫登陸的帳戶名稱，sa表示的是管理員帳戶名稱
             *  Password 表示數據庫登陸的密碼
             * 
             */
            // 如數據庫創建鏈接
            using (SqlConnection conn = new SqlConnection
                ("Data Source = 192.168.43.102; Initial Catalog = MyTest; User ID = sa; Password = 123"))
            {
                
                conn.Open();    // 打開數據庫
                /*
                 *  conn.CreateCommand  建立操做命令
                 *  cmd.CommandText     後面接的是sql語句
                 *  cmd.ExecuteNonQuery(); 實施查詢
                 *  
                 */

                using (SqlCommand cmd = conn.CreateCommand())  // 建立數據庫的操做指令信息
                {
                    // 操做數據庫的相關指令信息

                }
            }

insert 在 C# 的使用

一下是在wpf 中的Button按鈕對應的控制方法
,cs 文件內容以下：

/// <summary>
        /// 向數據庫寫入信息
        /// Insert語句的使用
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button_Click(object sender, RoutedEventArgs e)
        {
            // SqlConnection 繼承的父類 SqlConnection 實如今對自動回收接口的繼承
            // public abstract class DbConnection : Component, IDbConnection, IDisposable
            /* SqlConnection 實例化創建新的鏈接
             *  Data Source 表示 IP,若是是本機通訊的話，只須要寫 .  就能夠了
             *  Initial Catalog 對應的數據庫中將要操做的表格
             *  User ID 表示數據庫登陸的帳戶名稱，sa表示的是管理員帳戶名稱
             *  Password 表示數據庫登陸的密碼
             * 
             */
            using (SqlConnection conn = new SqlConnection
                ("Data Source = 192.168.43.102; Initial Catalog = MyTest; User ID = sa; Password = 123"))
            {
                
                conn.Open();    // 打開數據庫的鏈接
                /*
                 *  conn.CreateCommand  建立操做命令
                 *  cmd.CommandText     後面接的是sql語句
                 *  cmd.ExecuteNonQuery(); 實施查詢
                 *  
                 */
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "Insert into Table_Student(Name, Age, Height) Values ('Vs插入數據', 12, 12.1212)";
                    cmd.ExecuteNonQuery();

                }
                MessageBox.Show("寫入數據成功");

            }
        }

對應的
MainWindow.xaml文件以下

<Window x:Class="ShuJuKu15_ADONet_JiChu.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:ShuJuKu15_ADONet_JiChu"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Button x:Name="button" Content="寫入數據" HorizontalAlignment="Left" Margin="230,92,0,0" VerticalAlignment="Top" Width="75" Click="button_Click"/>
   
    </Grid>
</Window>

對應的界面以下

delete 的使用

對應的.cs文件

/// <summary>
        /// 數據庫刪除信息
        /// delete語句的使用
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btn_delete_Click(object sender, RoutedEventArgs e)
        {
            // SqlConnection 繼承的父類 SqlConnection 實如今對自動回收接口的繼承
            // public abstract class DbConnection : Component, IDbConnection, IDisposable
            using (SqlConnection conn = new SqlConnection
                ("Data Source = .; Initial Catalog = MyTest; User ID = sa; Password = 123"))
                //("Data Source = 192.168.43.102; Initial Catalog = MyTest; User ID = sa; Password = 123"))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "delete from Table_Student where Name ='aaa' ";
                    cmd.ExecuteNonQuery();

                }
                MessageBox.Show("刪除數據成功");

            }
        }

對應的.wpf文件

<Window x:Class="ShuJuKu15_ADONet_JiChu.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:ShuJuKu15_ADONet_JiChu"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Button x:Name="btn_delete" Content="刪除數據" HorizontalAlignment="Left" Margin="230,120,0,0" VerticalAlignment="Top" Width="75" Click="btn_delete_Click" />
    </Grid>
</Window>

對應的界面

其餘的操做同理。最後，融合在一塊兒後， 造成的界面以下：

對應的.wpf 文件以下

<Window x:Class="ShuJuKu15_ADONet_JiChu.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:ShuJuKu15_ADONet_JiChu"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Button x:Name="button" Content="寫入數據" HorizontalAlignment="Left" Margin="230,92,0,0" VerticalAlignment="Top" Width="75" Click="button_Click"/>
        <Button x:Name="btn_delete" Content="刪除數據" HorizontalAlignment="Left" Margin="230,120,0,0" VerticalAlignment="Top" Width="75" Click="btn_delete_Click" />
        <Button x:Name="btn_update" Content="更新數據" HorizontalAlignment="Left" Margin="230,150,0,0" VerticalAlignment="Top" Width="75" Click="btn_update_Click" />
        <Button x:Name="btn_queryAllLine" Content="查詢總行數" HorizontalAlignment="Left" Margin="363,92,0,0" VerticalAlignment="Top" Width="75" Click="btn_queryAllLine_Click"/>
        <Button x:Name="btn_writeAndReturnId" Content="寫入數據並方式對應的ID" HorizontalAlignment="Left" Margin="320,120,0,0" VerticalAlignment="Top" Width="150"  Click="btn_writeAndReturnId_Click"/>
   
    </Grid>
</Window>

對應的.cs文件以下

using System;
using System.Collections.Generic;
using System.Data.SqlClient;    // 數據庫空間引入
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace ShuJuKu15_ADONet_JiChu
{
    /// <summary>
    /// MainWindow.xaml 的交互邏輯
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }
        /// <summary>
        /// 向數據庫寫入信息
        /// Insert語句的使用
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button_Click(object sender, RoutedEventArgs e)
        {
            // SqlConnection 繼承的父類 SqlConnection 實如今對自動回收接口的繼承
            // public abstract class DbConnection : Component, IDbConnection, IDisposable
            /* SqlConnection 實例化創建新的鏈接
             *  Data Source 表示 IP,若是是本機通訊的話，只須要寫 .  就能夠了
             *  Initial Catalog 對應的數據庫中將要操做的表格
             *  User ID 表示數據庫登陸的帳戶名稱，sa表示的是管理員帳戶名稱
             *  Password 表示數據庫登陸的密碼
             * 
             */
            using (SqlConnection conn = new SqlConnection
                ("Data Source = 192.168.43.102; Initial Catalog = MyTest; User ID = sa; Password = 123"))
            {
                
                conn.Open();    // 打開數據庫的鏈接
                /*
                 *  conn.CreateCommand  建立操做命令
                 *  cmd.CommandText     後面接的是sql語句
                 *  cmd.ExecuteNonQuery(); 實施查詢
                 *  
                 */
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "Insert into Table_Student(Name, Age, Height) Values ('Vs插入數據', 12, 12.1212)";
                    cmd.ExecuteNonQuery();

                }
                MessageBox.Show("寫入數據成功");

            }
        }

        /// <summary>
        /// 數據庫刪除信息
        /// delete語句的使用
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btn_delete_Click(object sender, RoutedEventArgs e)
        {
            // SqlConnection 繼承的父類 SqlConnection 實如今對自動回收接口的繼承
            // public abstract class DbConnection : Component, IDbConnection, IDisposable
            using (SqlConnection conn = new SqlConnection
                ("Data Source = .; Initial Catalog = MyTest; User ID = sa; Password = 123"))
                //("Data Source = 192.168.43.102; Initial Catalog = MyTest; User ID = sa; Password = 123"))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "delete from Table_Student where Name ='aaa' ";
                    cmd.ExecuteNonQuery();

                }
                MessageBox.Show("刪除數據成功");

            }
        }
        /// <summary>
        /// 數據庫更新信息
        ///  update 語句的使用
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btn_update_Click(object sender, RoutedEventArgs e)
        {
            using (SqlConnection conn = new SqlConnection
                ("Data Source = 192.168.43.102; Initial Catalog = MyTest; User ID = sa; Password = 123"))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "update Table_Student set Age = 2 where Name ='Vs插入數據' ";
                    cmd.ExecuteNonQuery();

                }
                MessageBox.Show("更新數據成功");

            }
        }

        /// <summary>
        /// 數據庫查詢信息
        /// select 語句的應用
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btn_queryAllLine_Click(object sender, RoutedEventArgs e)
        {
            using (SqlConnection conn = new SqlConnection
                ("Data Source  = 192.168.43.102; Initial Catalog = MyTest; User ID = sa; Password = 123"))
            {
                int tmp = 0;
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "select count(*) from Table_Student ";
                    int i = (int)cmd.ExecuteScalar();   //ExecuteScalar通常用來執行有且只有一行一列返回值的SQL語句
                    tmp = i;
                    /*
                    //下面這段是查詢數據庫表格中是否有'aaa'並返回aaa
                    cmd.CommandText = "select 'aaa'";
                    //ExecuteScalar通常用來執行有且只有一行一列返回值的SQL語句
                    string s = (string)cmd.ExecuteScalar();
                    MessageBox.Show(s);
                    */
                }
                MessageBox.Show("總共有【" + tmp + "】條數據");
            }
        }

        /// <summary>
        /// 寫入數據庫中的表格並獲取ID
        /// insert 與 select ，及關鍵詞 @@identity ， output 的使用
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btn_writeAndReturnId_Click(object sender, RoutedEventArgs e)
        {
            // SqlConnection 繼承的父類 SqlConnection 實如今對自動回收接口的繼承
            // public abstract class DbConnection : Component, IDbConnection, IDisposable
            using (SqlConnection conn = new SqlConnection
                ("Data Source = 192.168.43.102; Initial Catalog = MyTest; User ID = sa; Password = 123"))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {

                    cmd.CommandText = "insert into Table_Student(Name, Age) values('bbb', 111)";
                    cmd.CommandText = "select Max(ID) as maxid Table_Student ";
                    string s = (string)cmd.ExecuteScalar();
                    MessageBox.Show(s);
                    //得到自字段的值
                    // @@ 是什麼意思
                    // 這段註釋一樣是寫入數據庫中的表格並獲取ID， 可是不是很好，由於這是，若是下寫入數據後，若是有新的數據
                    //忽然插進來寫入新的數據，這個時候獲取的ID就不是原來的ID ， 而是新的ID，這就不對了
                    cmd.CommandText = "insert into Table_Student(Name,Age) values('aaa',123) ;select @@identity";
                    decimal i = (decimal)cmd.ExecuteScalar();//

                    ////寫入數據並返回該數據對應的id值
                    //cmd.CommandText = "insert into Table_Student(Name,Age) output inserted.Id values('aaa',123) ";
                    //long i = (long)cmd.ExecuteScalar();//數據庫bigint→C#平臺long
                    MessageBox.Show(i.ToString());
                }
                MessageBox.Show("寫入數據成功");

            }
        }
    }
}