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如题
MySQL 使用 group by 之后然后 IFNULL(COUNT(*),0) 为什么还是会获得 null。
SELECT IFNULL(count(max_choose_number),0) FROM t_paper_**** tps WHERE tps.paper_id = 210 AND tps.structure_type = 4 GROUP BY tps.paper_id
结果为 null
闭关修行中......
In this case, there is generally no data that satisfies the where condition. Therefore, null is returned.
In this case, there is generally no data that satisfies the where condition. Therefore, null is returned.