this is really simple question.
I solved the two query question which can study aggregation method SUM and COUNT.
first of question : To learn COUNT.
summarize the statement : just count cities where have a population lager than 100,000.
checking point : before writting the SQL, need to think how can I solve this problem.
so, to count the cities, I need to use COUNT method and for checking the population, I need to use WHERE statement.
so this is my answer.
second of all : study SUM method.
summarize the statement : this question is same with before question.
but different point is that I need to use SUM method for getting total population about all citities especally California.
checking point : for solving this problem, I need to use SUM method.
so my answer is that
those are really simple questions.
just conside how to aggregate the column, and how to make the output on condition.
I will solve all of the questions in Hacker Rank cite step by step and I will explain it by Korean or English.
I will improve my skill every day.
jia you~!
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