oracle 动态游标 传参的问题

Question

declare type cur_type is ref cursor;
cur cur_type;
rec scott.emp%rowtype;
str varchar2(500):='';
letter char:='A';
begin loop
str:='select ename from scott.emp where ename like "%'||letter||'%" ';
open cur for str;
dbms_output.put_line('包含字母'||letter||'的名字');
loop fetch cur into rec.ename;
exit when cur%notfound;
dbms_output.put_line(rec.ename);
end loop;
exit when letter='Z';
letter:=chr(ascii(letter)+1);
end loop;
end;
------------------------------------------------------------------------
错误报告:
ORA-00904: "%A%": 标识符无效
ORA-06512: 在 line 8
00904. 00000 - "%s: invalid identifier"
*Cause:
*Action:
草 提的 问题 怎么删除。。。。。。。
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Answer 1

应该是这句有问题：
STR:='SELECT ENAME FROM SCOTT.EMP WHERE ENAME LIKE ''%'||LETTER||'%''';

Answer 2

letter char:='A';

改为
letter varchar2(2) :='A';

Answer 3

游标可以带变量声明
cursor cur(letter varchar2) is
select ename from scott.emp where ename like ‘%’||letter||'%'