Check if value exists in MySQL DB in Java?

Question

I'm creating a game right now that stores quest values into a DB when a player completes his or her quest. The issue I'm having right now is writing a method that searches the MySQL table for the player id and the quest id to check if he or she has already completed it.

I'm new to database programming in Java, so this was as far as I got by looking at some sample code elsewhere.

public boolean checkQuest(int questid) {
   Connection con = DatabaseConnection.getConnection();
   PreparedStatement ps = con.prepareStatement("SELECT questid FROM completedQuests WHERE characterid = ?");
   ps.setInt(1, scriptId);
   ResultSet rs = ps.executeQuery();

}

Basically, I want to check if the quest id exists in the table. If it doesn't, that means the player has yet to complete the quest and thus it is available.

Do you have a database already setup? Can you already connect to it? — Rey Libutan
– Rey Libutan, Commented Jun 16, 2015 at 6:26

Mureinik · Accepted Answer · 2015-06-16 06:27:41Z

6

I'd do this check in the where clause and use the Java side to simply check if this query returned any results:

Connection con = DatabaseConnection.getConnection();
PreparedStatement ps = 
    con.prepareStatement
    ("SELECT questid FROM completedQuests WHERE characterid = ? AND questid = ?");
ps.setInt (1, characterId);
ps.setInt (2, questId);
ResultSet rs = ps.executeQuery();

if (rs.next()) {
    // Quest already completed
} else {
    // Quest not completed yet
}

// Close resources etc.

answered Jun 16, 2015 at 6:27

Mureinik

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9 Comments

Jacob Macallan Over a year ago

What I originally intended was something of the sort where I pass a questid through a method parameter and check it to see if it exists in the DB. I don't think this does that comparison. My bad for unclarification. Or do I replace the ? with the parameter?

Mureinik Over a year ago

I fail to understand the question there. What is lacking from this solution?

Jacob Macallan Over a year ago

If I was to search for a specific quest id, would I substitute the "?"s with the specific questid?

Mureinik Over a year ago

@Xari no - you would set the PreparedStatement with it. That's what ps.setInt (2, questId); takes care of.

Mureinik Over a year ago

@Xari The "?" isn't a placeholder for you to replace, it's the way JDBC's syntax allows you to parameterize PreparedStatements.

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