ORA-01427执行count（*）时，单行子查询返回多行

Question

我正在运行以下查询进行计数并且它一直给我上述错误...

execute immediate 
  'select count(*) from "'||rec.table_name||'" WHERE "'||rec.column_name||'" LIKE ('''||l_str||''')' 
  into l_count;

最终结果是0或1，所以我不明白为什么会这么说。

完整的查询是：

SET SERVEROUTPUT ON size 30000;
declare
    l_count number := 0;
    l_str varchar2(20) := '%WORD%';
begin
    for rec in (select table_name, column_name
                from user_tab_columns
                where data_type in ( 'CLOB', 'VARCHAR', 'VARCHAR2', 'TEXT' )
               ) loop
        execute immediate
            'select count(*) from "'||rec.table_name||'" WHERE "'||rec.column_name||'" LIKE ('''||l_str||''')' 
            into l_count;
        if l_count > 0 then
            dbms_output.put_line('FOUND!!! - EXECUTE THIS: SELECT * FROM '||rec.table_name||' WHERE '||rec.column_name || ' LIKE'''||l_str||''';');
        end if;
    end loop;
end;
/
quit;