mysql group by 分组查询
分组的SQL语句有2个:group by 和分组聚合函数实现 partition by (oracle和postgreSQL中的语句)功能group by + having 组合赛选数据注意:having 条件的字段必须在前面查询赛选存在,否则语法错误错误格式:SELECT MAX(ID),U_ID FROM mlzm_comments GROUP BY U_ID HAVING Data_Status >0正确格式:SELECT MAX(ID),U_ID,..