mysql 根據date做年，月，日分組統計查詢

• 使用 YEAR(), MONTH(), DAY() 來獲取年月日

SELECT YEAR(application_date) as years, count(1) FROM patent GROUP BY YEAR(application_date) ORDER BY years

-- YEAR(application_date)   獲取年份
-- MONTH(application_date)　獲取月份
-- DAY(application_date)    獲取日

• 使用 date_format(application_date, '%Y')，可自定義日期格式

SELECT date_format(application_date, "%Y") as year, count(1) FROM patent GROUP BY date_format(application_date, "%Y")