Two onclick on one element

Two onclick on one element

I have a simple code to delete data from the database,and I want a warning
message to appear before deleting. the code works fine when I put one
onclick and when I put two only the first onclick works.
and I need to onclick one for the warning message and the other for
delet.php page.
<form><input type="button" value="delete" onclick="return confirm('Really
delete?');" onClick='window.location.href="delete.php?id= <?php echo $id;
?>"' ></form>