技術標籤：SQLZOO學習sql

1.Show the total number of prizes awarded.

SELECT COUNT(winner) 
FROM nobel

2.List each subject - just once

SELECT subject
FROM nobel
GROUP BY subject

3.Show the total number of prizes awarded for Physics.

SELECT COUNT(subject)
FROM nobel
WHERE subject = 'Physics'

4.For each subject show the subject and the number of prizes.

SELECT subject, COUNT(subject)
FROM nobel
GROUP BY subject

5.For each subject show the first year that the prize was awarded.

SELECT subject, MIN(yr)
FROM nobel 
GROUP BY subject

6.For each subject show the number of prizes awarded in the year 2000.

SELECT subject, COUNT(yr)
FROM nobel
WHERE yr = 2000
GROUP
 
 BY subject

7.Show the number of different winners for each subject.

SELECT subject, COUNT(DISTINCT(winner))
FROM nobel
GROUP BY subject
--每個winner獲獎會有重複，一定要記得DISTINCT之後再COUNT

8.For each subject show how many years have had prizes awarded.

SELECT subject, COUNT(DISTINCT(yr))
FROM nobel
GROUP BY subject
 

9.Show the years in which three prizes were given for Physics.

SELECT yr
FROM nobel
WHERE subject='Physics'
GROUP BY yr
HAVING COUNT(winner)=3
--篩選的是人獲得了三次獎項，分組與select要一致

10.Show winners who have won more than once.

SELECT winner
FROM nobel
GROUP BY winner
HAVING COUNT(*) > 1
--篩選要有對應的分組條件存在

11.Show winners who have won more than one subject

SELECT winner
FROM nobel
GROUP BY winner
HAVING COUNT(DISTINCT(subject)) > 1
--一個人可以獲得多種獎項，所以一定要DISTINCT之後再COUNT

12.Show the year and subject where 3 prizes were given. Show only years 2000 onwards.

SELECT yr, subject
FROM nobel
WHERE yr>=2000
GROUP BY yr, subject 
HAVING COUNT(*)=3
--刪選的是某個獎項獲得三次以上的年份