SUM, COUNT, MAX
and
AVG等の関数は"aggregates"(集合させる),これらは、クエリーの結果により、一つの数値として結果を返します。
(これらの関数はGROUP BY
と一緒に使うことにより、より使いやすくなる。)
Distinct
By default the result of a SELECT may contain duplicate rows.
We can remove these duplicates using the DISTINCT key word.
Order by
ORDER BY permits us to see the result of a SELECT in any
particular order. We may indicate ASC or DESC for ascending (smallest
first, largest last) or descending order.
1. The total population and GDP
of Europe.
Results
2. What are the regions?
Results
3. Show the name and population
for each country with
a population of more than 100000000. Show countries in descending order of
population.
