i created a table using mysql of users.
columns of the table are sequence, email, date\_created and date\_canceled.
primary is sequence and im trying to make a unique index for email and date\_canceled - so when email is active (never been canceled - means date\_canceled is NULL) there wont be another active email inserted or a situation of this happening.

i know its can be done with oracle db but with mysql unique indexs allow NULL.

any suggestions how to handle this??
thanks!