SQL

Question 1

sum by country, the results should be in new column

Answer 1

sum(stuff) over ( partition by country) as new_colum

Question 2

add two string together

Answer 2

concat(‘string1’,’string2’)

Question 3

make null results 0

Answer 3

nullif(column_name,0)

Question 4

row_number() over (partition by cast(created_at as date) order by created_at desc) as last_day

will be the biggest date or smallest date that rank 1?

Answer 4

Biggest! so the lates transation that day