sql多表查询时间段问题

我有3张表 rec200905
rec200906
rec200907
字段有：idnamedunit_Name(单位名) to_date(日期)
我要查的是rec200905表中时间在20090504

select * from rec200905 a,rec200906 b,rec200907 cwherea.ascertain>=to_date(&#39;2009-06-01 00:00:00&#39;,&#39;yyyy-mm-dd HH24:MI:SS&#39;) and c.ascertain<=to_date(&#39;2009-09-01 00:00:00&#39;,&#39;yyyy-mm-dd HH24:MI:SS&#39;) and a.unit_Name=b.unit_Name and b.unit_Name=c.unit_Name andc.unit_Name=&#39;技术部&#39; order by named

哪里不对呢？？
急......

order by named
哪个表的named？

select * from rec200905 a,rec200906 b,rec200907 cwherea.ascertain>=to_date(&#39;2009-06-01,&#39;yyyy-mm-dd&#39;) and c.ascertain<=to_date(&#39;2009-09-01&#39;,&#39;yyyy-mm-dd&#39;) and a.unit_Name=b.unit_Name and b.unit_Name=c.unit_Name andc.unit_Name=&#39;技术部&#39; order by named

这样就行了