使用另一个的count（*）值更新大表

I have two tables. Items has the fields id,title,number. The relevant field (list) in the other table (lists) is one with comma-separated values which are IDs from items. I want items.number to be the same as the count of times the relevant ID appears in the lists table. As an example, this query is working fine to achieve this...I have two tables. Items has the fields id,titl