Question

I hope that you can correct me if my syntax is wrong. I could check on Google only if the SELECT…WHERE clause is correct.

I want to retrieve the student_id for using it in another query, but seems that all I get from this is a “0”.

in java file:

rst = stmt.executeQuery("SELECT student_id FROM students WHERE name= 'to_delete'");
sid = rst.getInt("student_id");

to_delete is a String which this java file receives as a parameter to the method which must return student_id. It really contains the correct string(I checked it).

Table “students” contains the fileds: student_id, name, year. I need to have returned the student_id for the name “to_delete”.

I have no errors/exceptions, just that when I display the result, I see id: 0 no matter what name I type. Maybe rst.getString(“column_name”) is correct only for executeUpdate(…)?

Thank you in advance!

Answer 1

Call next() on the resultset before you try to get anything out of it. You iterate through the ResultSet by calling the next method every time you want to read a row. When next returns false you’re done.

Here’s the API documentation for the next method:

boolean next()
throws SQLException

Moves the cursor froward one row from its current position. A
ResultSet cursor is initially positioned before the first row; the
first call to the method next makes the first row the current row; the
second call makes the second row the current row, and so on.

When a call to the next method returns false, the cursor is positioned
after the last row. Any invocation of a ResultSet method which
requires a current row will result in a SQLException being thrown. If
the result set type is TYPE_FORWARD_ONLY, it is vendor specified
whether their JDBC driver implementation will return false or throw an
SQLException on a subsequent call to next.

If an input stream is open for the current row, a call to the method
next will implicitly close it. A ResultSet object’s warning chain is
cleared when a new row is read.

Returns:
true if the new current row is valid; false if there are no more rows Throws:
SQLException – if a database access error occurs or this method is called on a closed result set