you create a prepared statement, then fill in the variables with
values gleaned from java calls.

// With PreparedStatement, you leave ? where you come back later to
fill in the data.
// Update vendortimestamp field if the new value is bigger.
// Demonstrates use of the GREATEST function.
PreparedStatement stmt = conn.prepareStatement( "UPDATE vendors SET
vendorTimestamp=GREATEST(vendorTimestamp, ?), WHERE vendorId=?" );
stmt.setLong( 1, aPossiblyBiggerTimestamp );
stmt.setInt( 2, desiredVendorId );
stmt.executeUpdate();