java - java中的mysql选择查询

Question

我刚开始接触 java 和 mysql 数据库。我的查询有什么问题:

PreparedStatement statement = conn.prepareStatement("SELECT * FROM q_table, choices, answers  WHERE q_table.QID='" + number_input + "' AND choices.CID='" + number_input + "' AND answers.AID='" + number_input + "'");

Answer 1

在您的语句 "... q_table.QID='"+ number_input + "' AND ... 中，变量 number_input 包含在单引号 (' ). 这用于 string lieterals . 如果你删除单引号它应该工作:

 String prest= "SELECT * FROM q_table, choices, answers  WHERE questions.QID=? AND choices.CID=? AND answers.AID=?";

 prest.setInt(1,1980);
 prest.setInt(2,2004);
 .
 .
 ResultSet rs = prest.executeQuery();
 while (rs.next()){
     String mov_name = rs.getString(1);
     int mov_year = rs.getInt(2);
     count++;
     System.out.println(mov_name + "\t" + "- " + mov_year);
 }
 System.out.println("Number of records: " + count);
 prest.close();
 con.close();