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我有以下简单的代码来连接和查询与准备语句的数据库(它只是为了学习的目的)。JDBC PreparedStatement奇怪的行为
import java.sql.*;
public class Prepared {
public static void main(String[] args) throws SQLException,Exception {
Class.forName("com.mysql.jdbc.Driver");
Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/customerdb","myuser","luca01123581321");
String query="SELECT id,? FROM person WHERE id>=?";
PreparedStatement prep=conn.prepareStatement(query,ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_UPDATABLE);
prep.setString(1,"name");
prep.setInt(2,2);
prep.executeQuery();
ResultSet res=prep.getResultSet();
ResultSetMetaData rsmd=res.getMetaData();
System.out.println("number of columns: "+rsmd.getColumnCount());
while (res.next()) {
int id=res.getInt(1);
String name=res.getString(2);
System.out.println(name);
}
}
}
当我执行查询,并尝试打印结果我得到:
number of columns:2
name
name
name
name
换句话说
我想找回在第二列中的值(即“名”),其是SQL类型的VARCHAR。但不是获取所有记录的“名称”的值......那是怎么回事?