mysql 查询从表中获取计数

Question

我有 3 个这样的表:

Areas 
id      city_id         area
1       1               mayfield
2       2               cleveland

neighbourhood
id      neighbourhood   area_id
101     cayahoga        1
102     milan           1
103     downtown        2

Salons
id      neighbourhood_id
3       101
4       101
5       102

我正在尝试统计所有区域的所有沙龙。

喜欢地区的沙龙(梅菲尔德 = 2，克利夫兰 = 1)

是否可以在 1 个查询中完成此操作？

Answer 1

SELECT areas.area,COUNT(Salons.id)
FROM areas
LEFT JOIN neighbourhood ON neighbourhood.area_id = areas.id
LEFT JOIN Salons ON Salons.neighbourhood_id = neighbourhood.id
GROUP BY areas.id