Mysql相关查询

1.查询最新的分组倒序，最前几个

SELECT
            *
        FROM
            (
            SELECT
                max.*
            FROM
                ( SELECT DISTINCT a.* FROM t_journal_issue a WHERE a.if_delete = 1 ORDER BY a.release_time DESC ) max
            GROUP BY
                max.journal_id
            ) x
        ORDER BY
            x.release_time DESC

2.按组统计

SELECT
    publish_field_id AS id,
    count(*) AS count 
FROM
    t_article 
WHERE
    publish_field_id IS NOT NULL 
    AND LENGTH(trim(publish_field_id)) > 1  
GROUP BY
    publish_field_id