摘要:
如person表 pid,sid 两字段 用sid分组,结果如下:num sid5 00110 00212 0030 004select count(*) num,sid from person group by sid若求有多少组分组,如上例有四组,则select count(*) from (select count(*) num,sid from person group by sid )去除重复的项:select (distinct * ) from table 阅读全文