Question

我需要城市和这个城市的职位空缺数量。城市，简历，空缺 - 表。

这是我写的一个查询，但它不起作用（第二个左连接不起作用）

SELECT c.name city_name,
COUNT(v.id) vac_num, (r.id) res_num
FROM mnk_city c
LEFT JOIN mnk_vacancy
ON v.cityId = c.id
LEFT JOIN mnk_resume
ON c.id = r.cityId
GROUP BY c.name

Answer 1

SELECT c.name city_name,   
COUNT(v.id) vac_num, (r.id) res_num 
FROM mnk_city c 
LEFT JOIN mnk_vacancy v
ON v.cityId = c.id 
LEFT JOIN mnk_resume r 
ON c.id = r.cityId 
GROUP BY c.name

您缺少表别名。

Answer 2

似乎你缺少一些表别名 - mnk_vacancy应该跟随v，我可以看到，mnk_resume应该跟r。

SELECT c.name city_name,
COUNT(v.id) vac_num, (r.id) res_num
FROM mnk_city c
LEFT JOIN mnk_vacancy v
ON v.cityId = c.id
LEFT JOIN mnk_resume r
ON c.id = r.cityId
GROUP BY c.name

任何人都可以更正sql查询吗？

2 个答案: