GROUP by和WHERE不能一起工作

Question

为什么这段代码有效:

SELECT year, sum(value)
FROM test
GROUP BY year

这不是吗？

SELECT year, sum(value)
FROM test
GROUP BY year
WHERE `user` = 1

Answer 1

GROUP BY需要追求WHERE:

SELECT year, sum(value) FROM test WHERE user = 1 GROUP BY year