报错内容：sql 1093 - You can't specify target table 'u' for update in FROM clause
错误原因： if you're doing an UPDATE/INSERT/DELETE on a table, you can't reference that table in an inner query
解决方法： (you can however reference a field from that outer table...)
错误的sql语句
update gg_platform_navtree u set u.pid = (select id from gg_platform_navtree s where s.pid = u.pid and s.isleaf = 0 ) where u.isleaf = 1;
通过解决方案转换后的sql语句
update gg_platform_navtree u set u.pid = (select id from (select * from gg_platform_navtree) s where s.pid = u.pid and s.isleaf = 0 ) where u.isleaf = 1;