Generate script to export all tables in database

Select 'exp system/manager@database_name buffer=102400 feedback=10000 statistics=none grants=y FILE=d:\backup\'|| s.Owner|| '_' || s.Segment_Name||'.DMP LOG= d:\backup\'|| s.Owner|| '_' || s.Segment_Name||'.LOG TABLES=' || s.Owner|| '.' || s.Segment_Name
From Sys.Dba_Segments s, Sys.Dba_Data_Files f
Where f.Tablespace_Name = s.Tablespace_Name And f.File_Id = s.Header_File
And Segment_Type In ('TABLE PARTITION','TABLE')
And Owner In ('owner_name')
Group By s.Tablespace_Name, s.Owner, s.Segment_Name, s.Segment_Type, f.File_Name
Order By Round(Sum(s.Bytes) / 1024 / 1024, 2) Desc