Oracle 定义变量,该怎么处理

--这是我在SQL 2005中写的SQL：create table #tb(id int,tname nvarchar(10))insert into #tb    select 1,'x' union all    select 2,'y'begindeclare @i intselect @i =  count(1) from #tb where id=1 and tname='a'if @i = 0    begin        insert into #tb values (1,'a');        update #tb set tname='aa' where id=1 and tname='a'    endselect @i =  count(1) from #tb where id=2 and tname='y'if @i=0    begin        insert into #tb values (2,'y');        update #tb set tname='yy' where id=1 and tname='y'    endselect @i =  count(1) from #tb where id=1 and tname='c'if @i = 0    begin        insert into #tb values (1,'c');        update #tb set tname='cc' where id=1 and tname='c'    endendselect * from #tb