Imagine you're tasked with analysing user engagement for a mobile app $,$in December $2020$ and January $2021.$ The goal is to determine how well the app retains its user base during this period. In real$-$ life terms, retention rate is a crucial metric for app developers and businesses, as it reflects the percentage of users who continue using the app over time.

Note:$-$ Retention rate is the percentage of active users an account retains over a given period of time. In this case, assume the user is retained if he$/$she stays with the app in any future months. For example, if a user was active in Dec $2020$ and has activity in any future month, consider them retained for Dec. You can assume all accounts are present in Dec $2020$ and Jan $2021.$ Your output should have the account ID and the Jan $2021$ retention rate divided by the Dec $2020$ retention rate.

Table name:$-$ sf$\_$events

Tables Schema as Below:

sf$\_$events

columnName dataType

date DATE

account$\_$id VARCHAR$(50)$

user$\_$id VARCHAR$(50)$