假设：table_user：用户表（id, usename）table_planet：星球表（userid, people）[php]//子查询方式，不推荐，效率低SELECT name, (SELECT SUM(people) FROM table_planet WHERE userid=table_user.id) AS peopleCount FROM table_user//联合查询方式，推荐SELECT t1.username,SUM(t2.people) AS peopleCount??INNER JOIN table_user AS t1 ON t2.userid=t1.idFROM table_planet AS t2GROUP BY t2.userid[/php]
[php]select A.name , SUN(B.p_num) as num from usertable A inner join Startable B on A.u_id = B.u_idgroup by B.u_uid order by num desc;[/php]
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