Oracle数据库中，通过function的方式建立自增字段

 1 CREATE OR REPLACE FUNCTION "FUNC_NEXTID"
 2 (tablename in varchar2) return number is
 3 
 4   nextid number(12);
 5 begin
 6   begin
 7     select nvl(max(id),-1) into nextid from tSequence where upper(name) = upper(tablename);
 8   exception
 9     when no_data_found then nextid := 0;
10   end;
11 
12   if nextid = -1 then
13     INSERT INTO tSequence(name,id) VALUES(tablename,1);
14     nextid := 1;
15   else
16     update tSequence set id = id+1 where upper(name) = upper(tablename);
17     select nvl(max(id),-1) into nextid from tSequence where upper(name) = upper(tablename);
18   end if;
19 
20   return(nextid);
21 end FUNC_NEXTID;