标签:mysql sql postgresql
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;
我已经在价格和颜色列上有索引,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,自联接和窗口函数,但是无法弄清楚如何实现相同的结果.
任何建议非常感谢.
解决方法:
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' )
标签:mysql,sql,postgresql 来源: https://codeday.me/bug/20190721/1496810.html
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