摘要：1.按字段是否空分组，mysql数据库 SELECT SUM(t.PROJECT_UNIT_COUNT) AS PROJECT_UNIT_COUNT,COUNT(*) AS PROJECT_COUNTFROM QS_PROJECT t GROUP BY ISNULL(t.`xx`) 2.根据出生日期 阅读全文

摘要：1.截取字符串 left（str, length），right（str, length），substring（str, pos, length） 原文：http://www.jb51.net/article/27458.htm 2.显示查询结果的前100条 select * from tbl lim 阅读全文

摘要：select a.id as aid,b.id as bid,a.city,a.cang,a.sid,a.time as atime,b.time as btime,a.price as aprice,b.price as bprice,a.pm as apm,b.pm as bpm from (s 阅读全文