使SQL查询更有效

Question

如何使此SQL查询更有效？

SELECT 
  (SELECT COUNT(*) FROM table WHERE price < 10) AS priceUnder10,
  (SELECT COUNT(*) FROM table WHERE price BETWEEN 10 AND 20) AS price10to20,
  (SELECT COUNT(*) FROM table WHERE price > 20) AS priceOver20,
  (SELECT COUNT(*) FROM table WHERE colour = 'Red') AS colourRed,
  (SELECT COUNT(*) FROM table WHERE colour = 'Green') AS colourGreen,
  (SELECT COUNT(*) FROM table WHERE colour = 'Blue') AS colourBlue;

我已经在price和colour列上有索引,所以我正在寻找一种更好的方法来聚合数据.

我已经研究过使用GROUP BY,HAVING自连接和窗口函数,但无法弄清楚如何实现相同的结果.

任何建议非常感谢.

Answer 1

SELECT 
       COUNT(CASE WHEN price < 10 THEN 1 END) AS priceUnder10,
       COUNT(CASE WHEN price BETWEEN 10 AND 20 THEN 1 END) AS price10to20,
       COUNT(CASE WHEN price> 20 THEN 1 END) AS priceOver20,
       COUNT(CASE WHEN colour = 'Red' THEN 1 END) AS colourRed,
       COUNT(CASE WHEN colour = 'Green' THEN 1 END) AS colourGreen,
       COUNT(CASE WHEN colour = 'Blue' THEN 1 END) AS colourBlue
from YourTable  
WHERE price IS NOT NULL OR  colour IN ('Red','Green','Blue' )