mysql中利用联合查询批量处理数据(更新,查询,统计)语句

SELECT ask.id, count( answer.father_id ) , ask.answer_num
FROM `表名_ask` AS ask
LEFT JOIN `表名_answer` AS answer ON ask.id = answer.father_id
GROUP BY answer.father_id
ORDER BY ask.id ASC

UPDATE 表名_ask SET cityid =
(
    SELECT cityid
    FROM 表名
    WHERE 表名_ask.borough_id = 表名.id
    ORDER BY id ASC LIMIT 0, 1
)

UPDATE 表名_ask SET answer_num =
(
    SELECT count( 表名_answer.father_id )
 FROM `表名_answer`
 where 表名_ask.id = 表名_answer.father_id
 GROUP BY 表名_answer.father_id
 ORDER BY 表名_ask.id ASC
 LIMIT 0 , 1
)

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