Java sql ResultSet沒有數據

Question

我想從java中的sql數據庫中只提取一個數據。 我試圖使用resultSet，但是當我想將第一行exctract為int Variables時，它表示resultSet沒有內容。

這是我的代碼

try {

            statement = connexion.createStatement();
            statementArtist = connexion.createStatement();
            String artist = "Mac Miller";
            ResultSet resultat = statement.executeQuery("USE albums SELECT Album.numero_artist FROM Album INNER JOIN Artist ON Album.num_artist = Artiste.num_artist where name like '"+artist+"'");    
            int result = resultat.getInt(1); // Here is the problem
            String query = "USE albums INSERT INTO dbo.Album(Album.num_artist, title, price, genre, date, home, image) VALUES("
                    + result
                    + ", '"
                    + title
                    + "', "
                    + price
                    + ", '"
                    + genre
                    + "', '"
                    + date
                    + "', '"
                    + home
                    + "', '"
                    + image
                    + "')";
            statement.executeUpdate(query);

Answer 1

你應該在結果集上調用next()方法來“移動”迭代器：

...
ResultSet resultat = statement.executeQuery("USE albums SELECT Album.numero_artist FROM Album INNER JOIN Artist ON Album.num_artist = Artiste.num_artist where name like '"+artist+"'");    
resultat.next();           
int result = resultat.getInt(1); // Here is the problem
...

如果安全性和更好的性能對您的應用程序很重要，您還應該考慮使用預准備語句。

Answer 2

需要使用next（），也應該測試結果即

ResultSet resultat = statement.executeQuery("USE albums SELECT Album.numero_artist FROM Album INNER JOIN Artist ON Album.num_artist = Artiste.num_artist where name like '"+artist+"'");    
if (resultat.next()) {
    int result = resultat.getInt(1); // Here is the problem

也像“+ + artist +”'“容易出錯，例如，如果藝術家包含引號”'“你會得到大多數DB的Sql錯誤。最高使用Sql參數