java - 在这种情况下如何插入或更新数据库行

Question

我有一张 table

CREATE TABLE `category` (
  `category_id` int(11) ,
  `T1` varchar(50) DEFAULT NULL,
  `T2` varchar(50) DEFAULT NULL,
  `T3` varchar(50) DEFAULT NULL,
  `T4` varchar(50) DEFAULT NULL,
  `T5` varchar(50) DEFAULT NULL
 )

mysql> select * from category;
+-------------+----------+-------------+---------------+------+------+
| category_id | T1       | T2          | T3            | T4   | T5   |
+-------------+----------+-------------+---------------+------+------+
|         145 | Pop Corn | Regular Tub | Plain Salted  | NULL | NULL |
|         150 | Pop Corn | Buckets     | Plain Salted  | NULL | NULL | 
|         151 | Pop Corn | Jumbo       | Plain Salted  | NULL | NULL | 
|         152 | Pop Corn | Regular Tub | Butter Scotch | NULL | NULL | 
|         153 | Pop Corn | Regular Tub | Tomoto Tango  | NULL | NULL | 
|         154 | Pop Corn | Buckets     | Butter Scotch | NULL | NULL | 
|         222 | Pop Corn | NULL        | NULL          | NULL | NULL |
| +-------------+----------+-------------+---------------+------+-----

当我运行下面的程序时，它会在表中插入一条新记录，如下所示

223     Pop Corn | Buckets     | NULL          | NULL | NULL 

它实际上应该更新 category_id 222 的行，因为爆米花已经存在了

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class TestDate {
    public static void main(String[] args)
    {
        String  inputrequest = "Pop Corn@Buckets";
        String values[] = inputrequest.split("@");  
        String sqlselect = "";

        Connection dbConnection = null;
        PreparedStatement selectpst = null;
        ResultSet resultset = null;
        PreparedStatement selectpst2 = null;
        ResultSet resultset2 = null;
        String  sqlselect2 = "";

        Statement updateStatement  = null;

        // Length == 2
        if(values.length==2)
        {
            sqlselect = "select category_id  from category where T1 = ? AND T2 = ? AND T3 IS NULL"  
            selectpst = dbConnection.prepareStatement(sqlselect);
            selectpst.setString(1, values[0]);
            selectpst.setString(2, values[0]);
            resultset = selectpst.executeQuery();
            if(resultset.next())
            {
                System.out.println("Already exists");
            }
            else
            {
                sql = "Insert into category (T1,T2,T3,T4,T5) values ('"+values[0]+"','"+values[1]+"',NULL,NULL,NULL) ";
                updateStatement.executeUpdate(sql);
            }

        }
}
}

谁能帮我解决这个问题？？

Answer 1

你的参数设置错误:

selectpst.setString(1, values[0]);
selectpst.setString(2, values[0]);

我认为应该是:

selectpst.setString(1, values[0]);
selectpst.setString(2, values[1]);