Calculating Cumulative Percentages in SQL

I have this table (myt) :

Identifying Pairs of People that had Covid-19

I have this table (myt) about people that had Covid-19:

Calculating average number of days between two events

I have this table in SQL (called “myt”) about library books that are borrowed by different names:

Keeping the entire set of duplicates with the highest year (per name)

I have this table in SQL:

SQL: Keeping the entire set of duplicates with the highest year (per name)

I have this table in SQL:

Dividing Overlapping Periods in SQL

I have this table in SQL (called “df”):

Analyzing Gap Years in SQL

I have a table (myt) in SQL that looks like this:

Insert new line AND update old column

I am not sure if i can archive this with a merge, because sometime i read that you can update AND insert and sometimes i read, that you can update OR insert.

Creating a Cumulative Table in SQL

I have these 3 tables :

Checking for Differences between Tables and Making Changes

I have these two tables: