Moves a relative number of rows, either positive or negative. Attempting to move beyond the first/last row in the result set positions the cursor before/after the the first/last row. Calling relative(0) is valid, but does not change the cursor position.
Note: Calling relative(1) is different than calling next() since is makes sense to call next() when there is no current row, for example, when the cursor is positioned before the first row or after the last row of the result set.
Reimplemented in com::mysql::jdbc::UpdatableResultSet.