Troubled with PreparedStatement, please help

Question

Hello all:
Here is a seemingly too simple a problem which is already taking my day. Please help.
String x=null;
String querry1 = null;
String querry2 = null;
ResultSet rs = null;
Statement st = null;
PreparedStatement pstmt = null;
try {
st = conn.createStatement();
//MAKE FIRST QUERRY
querry1 = "SELECT * FROM table1 WHERE (a= ? OR b = ?)";
pstmt = conn.prepareStatement(querry1);
pstmt.setString(1, userInput);
pstmt.setString(2, userInput);
rs = pstmt.executeQuery();
while(rs.next()){
//Process the result set.
//The value of x is one of the values in the result set.
//Hence get it.
x = rs.getString("C");
     }//end while
//No problem up to here.
//For check, output the value of x
System.out.println(x); //correct non-null value is displayed
//MAKE SECOND QUERRY based on the value of 'x'
querry2 = "SELECT * FROM table2 WHERE C= ? ";
//Table 1 and table 2 have a common column C.
//I want to retrieve the value from table 2 for which C=x;
pstmt = conn.prepareStatement(querry2);
pstmt.setString(1, x);
rs = pstmt.executeQuery();
//The problem is that in this 2nd querry, SQL error is caught, with the message
"java.sql.SQLException: Illegal operation on empty result set"
//whereas it should have produced a valid value.
//When the querry is formed explicitly (as follows), there is no problem. Result set is OK.
//when the value of x is "mystring", then the follwoing 3 lines work
pstmt = conn.prepareStatement(querry2);
pstmt.setString(1, "mystring");
rs = pstmt.executeQuery();
Please teach me what the hell I'm not getting here.
Thank you.

Answer 1

I would have thought you'd get this exception:
"java.sql.SQLException: Illegal operation on empty result set"
because you're trying to call something like:
rs.getString("foo");on an empty ResultSet. You can test whether the ResultSet has any rows as ResultSet.next() returns a boolean value, i.e.:
if (rs.next())
    rs.getString("foo");
}So the question is why is your second ResultSet empty? Maybe the value of C you are getting from table1 has leading/trailing whitespace that is not in table2?