没有group by子句，只返回1条记录；其中，返回所需的记录数

SELECT PM.id AS id, PM.email AS email, PM.name AS name, PM.mobile AS mobile, PM.country AS country, PM.status AS status, PM.cdate AS joined_date, PM.details_status AS details_status, PM.freeze AS freeze, PM.blacklist AS blacklist, PM.blacklist_remark AS blacklist_remark, PM.blacklist_adate AS blacklist_adate, MA.m_app_id AS app_id, MA.full_name AS replace_name, MAX(MA.ldate) AS ldate, MA.service_type AS svc_type FROM whatever_db.tw_person_merchant PM LEFT JOIN ( whatever_db.tw_person_merchant PMM INNER JOIN whatever_db.tw_merchant_application_details MA ON PMM.app_id = MA.m_app_id INNER JOIN whatever_db.tw_merchant_application MAP ON MA.m_app_id = MAP.id AND MAP.status NOT IN ('10' , '60') AND MA.id = (SELECT max(id) FROM whatever_db.tw_merchant_application_details WHERE m_app_id = PMM.app_id ) ) ON PM.app_id = MA.m_app_id WHERE PM.details_status IN ('90', '0') AND PM.blacklist = 0 AND PM.name != '' -- **here, without the group by clause, the result is just 1 record GROUP BY PM.id ORDER BY PM.id DESC

我正在测试sql脚本是否有相关商家返回，但中间只显示1条记录，经过反复试验，插入的“group by”解决了这个问题。但这个“group by”不是总结，而是显示比没有它更多的结果。意想不到的结果和如此背叛理智的行为。