如何使用列不同的方法得到列数，列名，列的类型等？

解决方法

下面的示例使用getColumnCount，getColumnName，getColumnTypeName，getColumnDisplaySize方法来获取没有列在表中的列的列或类型的名称。

import java.sql.*;

public class jdbcConn {
   public static void main(String[] args) throws Exception{
      Class.forName("org.apache.derby.jdbc.ClientDriver");
      Connection con = DriverManager.getConnection
      ("jdbc:derby://localhost:1527/testDb","name","pass");
      Statement stmt = con.createStatement();
      String query = "select * from emp order by name";
      ResultSet rs = stmt.executeQuery(query);
      ResultSetMetaData rsmd = rs.getMetaData();
      System.out.println("no of columns in the table= "+
      rsmd.getColumnCount());
      System.out.println("Name of the first column "+ 
      rsmd.getColumnName(1));
      System.out.println("Type of the second column "+
      rsmd.getColumnTypeName(2));
      System.out.println("No of characters in 3rd column "+ 
      rsmd.getColumnDisplaySize(2));
   }
}

结果

上面的代码示例将产生以下结果。该结果可能会不同。

no of columns in the table= 3
Name of the first columnID
Type of the second columnVARCHAR
No of characters in 3rd column20