Question

我试图存储消息，所以我用HeidiSql在mysql中创建了2个表，第一个是msg，第二个是用户。我写了一个存储过程来获取作为发送者的第一个参数的消息数，作为第二个参数的接收者，反之，我将此值存储在id变量中。我需要变量来计算2个人之间的消息。当我从java运行应用程序时，我总是得到id = 0。我无法理解这个错误。

...

sql="call getIdMsg(?,?,?)";
sql2="call addRecord(?,?,?,?)";

try (Connection conn= DriverManager.getConnection(db_url,username,password);
         CallableStatement statement = conn.prepareCall(sql);
         CallableStatement statement2 = conn.prepareCall(sql2)){

        statement.setInt(1,sender);
        System.out.println(sender);
        statement.setInt(2,recipient);
        System.out.println(recipient);
        statement.registerOutParameter(3, Types.INTEGER);
        statement.execute();
        id=statement.getInt(3);

        System.out.println("ID is: "+id);

        statement2.setInt(1,sender);
        statement2.setInt(2,recipient);
        statement2.setInt(3,id);
        statement2.setString(4,msg);
        statement2.execute();
        System.out.println("The record is been added");
    }
    catch (SQLException sqle){sqle.printStackTrace();}
...

这是我的sql代码：

BEGIN
set @id = ((select count(*) from msg WHERE sender = @thisrecipient and recipient = @thissender)+(SELECT COUNT(*) FROM msg WHERE sender = @thissender and recipient = @thisrecipient));
END

这些是我的参数：

thissender INT IN
此收件人INT IN
id INT OUT

你能帮我吗？

选择count返回0 mysql JDBC

0 个答案: