Aggregates with DISTINCT/ja

Language:Project:Language policy	English  • 日本語

COUNT DISTINCT

COUNTとDISTINCTを併用すると異なる値の個数が分かる

1915年は異なる3分野で4人が受賞した:

SELECT yr, subject, winner FROM nobel WHERE yr=1915

yr subject winner 1915 Chemistry Richard Willstätter 1915 Literature Romain Rolland 1915 Physics Lawrence Bragg 1915 Physics William Bragg

COUNT(subject) の値は 4; COUNT(DISTINCT subject) の値は 3.

SELECT COUNT(subject), COUNT(DISTINCT subject)
  FROM nobel
 WHERE yr = 1915

SELECT COUNT(subject), COUNT(DISTINCT subject)
  FROM nobel
 WHERE yr = 1915