Java ResultSet how to check if there are any resul

Question

Resultset has no method for hasNext. I want to check if the resultSet has any value

is this the correct way

if (!resultSet.next() ) {
    System.out.println("no data");
} 

Answer 1

That would work if you want to see if there are any rows in the result set yes.

Note that next() always moves to the next row, so if you are planning on doing any reading from the result set you need to take that into account.

Usual usage with ResultSet (when simply reading) is:

while (resultSet.next())
{
   ... read from the row here ...
}

Which obviously won't work correctly if you invoked next() once already to check if the result set was empty, so watch out for that. Although there are methods for "backing up", they are not supported for all types of result sets.

Answer 2

I've been attempting to set the current row to the first index (dealing with primary keys). I would suggest

if(rs.absolute(1)){
    System.out.println("We have data");
} else {
    System.out.println("No data");
}

When the ResultSet is populated, it points to before the first row. When setting it to the first row (indicated by rs.absolute(1)) it will return true denoting it was successfully placed at row 1, or false if the row does not exist. We can extrapolate this to

for(int i=1; rs.absolute(i); i++){
    //Code
}

which sets the current row to position i and will fail if the row doesn't exist. This is just an alternative method to

while(rs.next()){
    //Code
}

Answer 3

According to the most viable answer the suggestion is to use "isBeforeFirst()". That's not the best solution if you don't have a "forward only type".

There's a method called ".first()". It's less overkill to get the exact same result. You check whether there is something in your "resultset" and don't advance your cursor.

The documentation states: "(...) false if there are no rows in the result set".

if(rs.first()){
    //do stuff      
}

You can also just call isBeforeFirst() to test if there are any rows returned without advancing the cursor, then proceed normally. – SnakeDoc Sep 2 '14 at 19:00

However, there's a difference between "isBeforeFirst()" and "first()". First generates an exception if done on a resultset from type "forward only".

Compare the two throw sections: http://docs.oracle.com/javase/7/docs/api/java/sql/ResultSet.html#isBeforeFirst() http://docs.oracle.com/javase/7/docs/api/java/sql/ResultSet.html#first()

Okay, basically this means that you should use "isBeforeFirst" as long as you have a "forward only" type. Otherwise it's less overkill to use "first()".

Answer 4

This is a practical and easy read piece I believe.

        if (res.next()) {
            do {

                // successfully in. do the right things.

            } while (res.next());
        } else {
           // no results back. warn the user.
        }

Answer 5

ResultSet rs = rs.executeQuery();
if(rs.next())
{
  rs = rs.executeQuery();
  while(rs.next())
  {
    //do code part
  }
}
else
{
  //else if no result set
}

It is better to re execute query because when we call if(rs.next()){....} first row of ResultSet will be executed and after it inside while(rs.next()){....} we'll get result from next line. So I think re-execution of query inside if is the better option.

Answer 6

ResultSet result = stmt.executeQuery(sqlQuery);
if (!result.next())
    status = "ERROR";
else
    status = "SUCCESS";