SELECT
`_conf_cities`.`cityid`,
`_conf_cities`.`countryid`,
`_conf_cities`.`name_mkd`,
`_conf_cities`.`child_municipality`,
`_conf_cities`.`parent`,
`conf_countries`.`countryid`,
`conf_countries`.`alpha2`
FROM `_conf_cities`
LEFT JOIN `conf_countries` ON `_conf_cities`.`countryid` = `conf_countries`.`countryid`
LEFT JOIN `_conf_cities` ON `_conf_cities`.`cityid` = `_conf_cities`.`parent`
WHERE `_conf_cities`.`child_municipality` = '0'
当我尝试LEFT JOIN _conf_cities自身时，就会出现问题。
可以用其他方式完成吗？
最佳答案
您必须使用别名，例如:
SELECT
_conf_cities.cityid,
_conf_cities.countryid,
_conf_cities.name_mkd,
_conf_cities.child_municipality,
_conf_cities.parent,
conf_countries.countryid,
conf_countries.alpha2,
t2.cityid -- Now you can use alias
FROM _conf_cities
LEFT JOIN conf_countries ON _conf_cities.countryid = conf_countries.countryid
LEFT JOIN _conf_cities AS t2 ON _conf_cities.cityid = t2.parent
WHERE
_conf_cities.child_municipality = '0'
AND t2.child_municipality = '0' -- Also you can use alias here
关于mysql - 同一个表内的Left Join SQL，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/45942601/