我在Oracle SQL数据库中有一个这样的函数

create or replace function DEF_ID(
in_checkid IN SQLTEXTDEFN.SQLID%type
) 
return varchar2
as
sql_stmt clob;
ret varchar2(254);
begin
   begin 
     execute immediate 'select SQLTEXT from SQLTEXTDEFN where sqlid=:1'
         into sql_stmt
         using in_checkid;
       begin
         execute immediate sql_stmt into ret;
         EXCEPTION
                WHEN NO_DATA_FOUND THEN
                    RETURN 'NO DATA FOUND';
                when others then
                    return substr(sqlerrm,1,200);
       end; 
            EXCEPTION
                WHEN NO_DATA_FOUND THEN
                    RETURN 'NO CHECK FOUND';
                when others then
                    return substr(sqlerrm,1,200);
            END;
return ret;
end;

SQLTEXTDEFN表是一个包含不同SQL语句的表。当我执行此函数时，会得到SQL语句的响应。在某些情况下，我会得到一个错误：

ORA-01422: exact fetch returns more than requested number of rows

如果获取多行，我只希望第一行作为结果。