String sql = "UPDATE edit SET new_text = ? WHERE edit_name=111";

这是一个更新 SQL 语句，将 edit 表中 edit_name 为 111 的记录的 new_text 字段更新为指定的值。其中的问号是占位符，需要使用 PreparedStatement 对象来执行该 SQL 语句，并将实际的值传入问号对应的位置。具体的代码可能如下：

String sql = "UPDATE edit SET new_text = ? WHERE edit_name=111";
try (Connection conn = DriverManager.getConnection(url, user, password);
     PreparedStatement pstmt = conn.prepareStatement(sql)) {
    pstmt.setString(1, "new value"); // 将问号替换为指定的值
    int rows = pstmt.executeUpdate(); // 执行更新操作
    System.out.println(rows + " rows updated."); // 输出更新的行数
} catch (SQLException e) {
    e.printStackTrace();
}

相关问题

用PHP代码实现学生选课管理系统

好的，我可以为您提供一个简单的PHP代码实现学生选课管理系统的示例。以下是一些基本功能：

1. 学生可以注册账户，登录系统。
2. 学生可以浏览可选的课程列表，并选择感兴趣的课程。
3. 管理员可以添加、删除和编辑课程列表。
4. 学生可以查看他们已经选择的课程，并取消选择。
5. 管理员可以查看每门课程的选课情况，包括已经选择该课程的学生列表。

以下是实现这些功能的PHP代码示例：

1. 注册账户和登录系统

//连接数据库
$conn = mysqli_connect("localhost", "username", "password", "database");

//注册账户
if(isset($_POST['register'])){
    $username = mysqli_real_escape_string($conn, $_POST['username']);
    $password = mysqli_real_escape_string($conn, $_POST['password']);
    $sql = "INSERT INTO users (username, password) VALUES ('$username', '$password')";
    mysqli_query($conn, $sql);
}

//登录系统
if(isset($_POST['login'])){
    $username = mysqli_real_escape_string($conn, $_POST['username']);
    $password = mysqli_real_escape_string($conn, $_POST['password']);
    $sql = "SELECT * FROM users WHERE username='$username' AND password='$password'";
    $result = mysqli_query($conn, $sql);
    if(mysqli_num_rows($result) == 1){
        //登录成功，跳转到主页
        header("location: index.php");
    } else {
        echo "用户名或密码错误！";
    }
}

2. 浏览可选的课程列表和选择课程

//获取可选的课程列表
$sql = "SELECT * FROM courses";
$result = mysqli_query($conn, $sql);

//显示课程列表
while($row = mysqli_fetch_assoc($result)){
    echo "<p>".$row['course_name']."<br>".$row['course_description']."<br>";
    //判断当前用户是否已经选择该课程
    $sql2 = "SELECT * FROM selections WHERE user_id=$user_id AND course_id=".$row['course_id'];
    $result2 = mysqli_query($conn, $sql2);
    if(mysqli_num_rows($result2) == 0){
        echo "<a href='select.php?course_id=".$row['course_id']."'>选择</a></p>";
    } else {
        echo "已选择</p>";
    }
}

//选择课程
if(isset($_GET['course_id'])){
    $course_id = $_GET['course_id'];
    $sql = "INSERT INTO selections (user_id, course_id) VALUES ($user_id, $course_id)";
    mysqli_query($conn, $sql);
    header("location: index.php");
}

3. 添加、删除和编辑课程列表

//添加课程
if(isset($_POST['add'])){
    $course_name = mysqli_real_escape_string($conn, $_POST['course_name']);
    $course_description = mysqli_real_escape_string($conn, $_POST['course_description']);
    $sql = "INSERT INTO courses (course_name, course_description) VALUES ('$course_name', '$course_description')";
    mysqli_query($conn, $sql);
}

//删除课程
if(isset($_GET['delete'])){
    $course_id = $_GET['delete'];
    $sql = "DELETE FROM courses WHERE course_id=$course_id";
    mysqli_query($conn, $sql);
}

//编辑课程
if(isset($_POST['edit'])){
    $course_id = mysqli_real_escape_string($conn, $_POST['course_id']);
    $course_name = mysqli_real_escape_string($conn, $_POST['course_name']);
    $course_description = mysqli_real_escape_string($conn, $_POST['course_description']);
    $sql = "UPDATE courses SET course_name='$course_name', course_description='$course_description' WHERE course_id=$course_id";
    mysqli_query($conn, $sql);
}

4. 查看已选择的课程和取消选择

//获取已选择的课程列表
$sql = "SELECT courses.course_name, courses.course_description FROM selections JOIN courses ON selections.course_id=courses.course_id WHERE selections.user_id=$user_id";
$result = mysqli_query($conn, $sql);

//显示已选择的课程列表
while($row = mysqli_fetch_assoc($result)){
    echo "<p>".$row['course_name']."<br>".$row['course_description']."<br>";
    echo "<a href='cancel.php?course_name=".$row['course_name']."'>取消选择</a></p>";
}

//取消选择
if(isset($_GET['course_name'])){
    $course_name = $_GET['course_name'];
    $sql = "DELETE FROM selections WHERE user_id=$user_id AND course_id=(SELECT course_id FROM courses WHERE course_name='$course_name')";
    mysqli_query($conn, $sql);
    header("location: index.php");
}

5. 查看每门课程的选课情况

//获取每门课程的选课情况
$sql = "SELECT courses.course_name, COUNT(selections.user_id) AS num_students FROM selections JOIN courses ON selections.course_id=courses.course_id GROUP BY courses.course_id";
$result = mysqli_query($conn, $sql);

//显示每门课程的选课情况
while($row = mysqli_fetch_assoc($result)){
    echo "<p>".$row['course_name'].": ".$row['num_students']."人选择</p>";
}

这些代码只是一个简单的示例，可能需要根据您的具体需求进行修改。希望对您有所帮助！

我要从access数据库中获取指定表的数据实时更新excel中，之后我再excel中更新数据，access也要同时更新，最加，删除，筛选查询等功能的vba代码

以下是将 Access 数据库中的数据实时更新到 Excel 中，以及在 Excel 中更新数据时同时更新 Access 数据库的 VBA 代码示例：

1. 将 Access 数据库中的数据实时更新到 Excel 中：

Sub UpdateAccessData()
    Dim conn As ADODB.Connection
    Dim rs As ADODB.Recordset
    Dim sql As String
    Dim i As Integer
    Dim fieldCount As Integer
    
    ' 连接 Access 数据库
    Set conn = New ADODB.Connection
    conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=your_access_database_path;"
    conn.Open
    
    ' 查询数据
    sql = "SELECT * FROM your_table_name;"
    Set rs = New ADODB.Recordset
    rs.Open sql, conn
    
    ' 将数据写入 Excel
    fieldCount = rs.Fields.Count
    For i = 0 To fieldCount - 1
        Worksheets("Sheet1").Cells(1, i + 1).Value = rs.Fields(i).Name
    Next i
    Worksheets("Sheet1").Range("A2").CopyFromRecordset rs
    
    ' 清理资源
    rs.Close
    conn.Close
    Set rs = Nothing
    Set conn = Nothing
End Sub

2. 在 Excel 中更新数据时同时更新 Access 数据库：

Sub UpdateAccessDatabase()
    Dim conn As ADODB.Connection
    Dim rs As ADODB.Recordset
    Dim sql As String
    Dim i As Integer
    Dim fieldCount As Integer
    Dim rowCount As Integer
    
    ' 连接 Access 数据库
    Set conn = New ADODB.Connection
    conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=your_access_database_path;"
    conn.Open
    
    ' 查询数据
    sql = "SELECT * FROM your_table_name;"
    Set rs = New ADODB.Recordset
    rs.Open sql, conn
    
    ' 更新数据
    fieldCount = rs.Fields.Count
    rowCount = rs.RecordCount
    Worksheets("Sheet1").Range("A2").CopyFromRecordset rs
    For i = 0 To rowCount - 1
        rs.MoveFirst
        rs.Move i
        rs.Edit
        rs.Fields("your_field_name").Value = Worksheets("Sheet1").Cells(i + 2, "A").Value
        ' 其他字段的更新
        rs.Update
    Next i
    
    ' 清理资源
    rs.Close
    conn.Close
    Set rs = Nothing
    Set conn = Nothing
End Sub

3. 添加最加、删除、筛选查询等功能：

最加数据：

Sub AddDataToAccessDatabase()
    Dim conn As ADODB.Connection
    Dim rs As ADODB.Recordset
    Dim sql As String
    
    ' 连接 Access 数据库
    Set conn = New ADODB.Connection
    conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=your_access_database_path;"
    conn.Open
    
    ' 添加数据
    sql = "INSERT INTO your_table_name (your_field1_name, your_field2_name, ...) VALUES (value1, value2, ...);"
    conn.Execute sql
    
    ' 清理资源
    conn.Close
    Set conn = Nothing
End Sub

删除数据：

Sub DeleteDataFromAccessDatabase()
    Dim conn As ADODB.Connection
    Dim rs As ADODB.Recordset
    Dim sql As String
    
    ' 连接 Access 数据库
    Set conn = New ADODB.Connection
    conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=your_access_database_path;"
    conn.Open
    
    ' 删除数据
    sql = "DELETE FROM your_table_name WHERE your_field_name=value;"
    conn.Execute sql
    
    ' 清理资源
    conn.Close
    Set conn = Nothing
End Sub

筛选查询：

Sub FilterDataFromAccessDatabase()
    Dim conn As ADODB.Connection
    Dim rs As ADODB.Recordset
    Dim sql As String
    
    ' 连接 Access 数据库
    Set conn = New ADODB.Connection
    conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=your_access_database_path;"
    conn.Open
    
    ' 筛选数据
    sql = "SELECT * FROM your_table_name WHERE your_field_name=value;"
    Set rs = New ADODB.Recordset
    rs.Open sql, conn
    
    ' 将数据写入 Excel
    Worksheets("Sheet1").Range("A2").CopyFromRecordset rs
    
    ' 清理资源
    rs.Close
    conn.Close
    Set rs = Nothing
    Set conn = Nothing
End Sub

希望这些代码可以帮助你实现你的需求。请根据自己的实际情况进行修改。