How does Oracle read CLOB data?

In Oracle, you can use the following methods to read CLOB data:

Utilize the SELECT statement and functions from the DBMS_LOB package to retrieve CLOB data. Here is an example:

DECLARE
  clob_data CLOB;
BEGIN
  SELECT clob_column INTO clob_data FROM your_table WHERE id = your_id;
  DBMS_OUTPUT.PUT_LINE(clob_data);
END;

2. Implementing PL/SQL cursor to retrieve CLOB data. Here is an example:

DECLARE
  clob_data CLOB;
  cursor c1 is SELECT clob_column FROM your_table WHERE id = your_id;
BEGIN
  open c1;
  fetch c1 into clob_data;
  close c1;

  DBMS_OUTPUT.PUT_LINE(clob_data);
END;

3. Use JDBC driver in Java or other programming language to read CLOB data. Here is an example:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class ReadClobData {
   public static void main(String[] args) {
      try {
         // 连接到数据库
         Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE", "username", "password");

         // 准备SQL语句
         String sql = "SELECT clob_column FROM your_table WHERE id = ?";
         PreparedStatement stmt = conn.prepareStatement(sql);
         stmt.setInt(1, your_id);

         // 执行查询
         ResultSet rs = stmt.executeQuery();
         if (rs.next()) {
            // 读取CLOB数据
            java.sql.Clob clobData = rs.getClob(1);
            String clobString = clobData.getSubString(1, (int) clobData.length());
            System.out.println(clobString);
         }

         // 关闭连接
         rs.close();
         stmt.close();
         conn.close();
      } catch (Exception e) {
         e.printStackTrace();
      }
   }
}

Please note that the examples above are for demonstration purposes only and do not take into account error handling. In actual use, please modify and handle securely according to the specific situation.