关于mysql单一表2次查询语句有关问题

SELECT t1.tongji FROM tab1 t1 LEFT JOIN tab1 t2 ON t1.AID=t2.FAID WHERE t2.AID=3

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查询湖北的tongji字段：
SELECT tongji FROM Tab1 WHERE AREA='湖北'

查询aid是3的父栏的tongji字段
SELECT tongji FROM Tab1 WHERE aid IN (SELECT faid FROM Tab1 WHERE aid=3)