mysql分组统计班级人数及批量修改收据编号

批量修改收据编号

update `sj_main` set `jf_id`=concat('202100',SUBSTRING(`jf_id`, -4));
update `sj_mx` set `sj_id`=concat('202100',SUBSTRING(`sj_id`, -4))

分组统计班级人数

SELECT COALESCE (`banji`, '合计') as '班级', COUNT(`id`) '班级学生数' FROM `youtable` where `zaixiao`='1' GROUP BY `banji` WITH ROLLUP