MySQl grouping displays the top N items in the group and deletes duplicates to retain the largest id data

separate query

 

first query id

select CAST(group_concat(ids) AS CHAR(10000) CHARACTER SET utf8) as iid 

from (select SUBSTRING_INDEX(group_concat(id ORDER BY 字段),',',4) as ids from `table` group by 字段) as val

query data by id

SELECT * FROM table where id in ($id)

 

This is also possible

select field,substring_index(group_concat( concat(field,':',field) order by field desc separator '|'),'|',5) from table group by field;

Depending on the situation

DELETE FROM xxx WHERE id NOT IN(SELECT id FROM (SELECT MAX(b.id) AS id FROM xxx b GROUP BY b.xxxx) b)

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