SQL会先执行from语句，然后where，然后是select

SELECT DISTINCT t1.`店铺链接`, t1.`店铺名称`, t1.`平台`
FROM sales AS t1 INNER JOIN shopinfo AS t2 ON t1.`店铺链接` = t2.`店铺链接`
WHERE t2.`省` = "河南";

没问题

 

下边的会报错，1054 - Unknown column 'sales.店铺链接' in 'field list'

SELECT DISTINCT  sales.`店铺链接`, sales.`店铺名称`, sales.`平台`
FROM sales AS t1 INNER JOIN shopinfo AS t2 ON t1.`店铺链接` = t2.`店铺链接`
WHERE t2.`省` = "河南";