一个关于SQL的奇怪问题

[hnzsy]

本人一个ORALCE存储过程中有这样一条语句：
。。。。。
a number(10);

SERV_ID:= 424858;
ACCT_ITEM_TYPE_ID := 'A21';

select count(*)
into a
ORDER_SERIAL_NBR
from serv_acct
where (eff_date = (select max(eff_date) from serv_acct where serv_id = SERV_ID and acct_item_type_id = ACCT_ITEM_TYPE_ID)) and
(serv_id = SERV_ID and acct_item_type_id = ACCT_ITEM_TYPE_ID);

执行后 a = 2

但是我把此语句放在SQLPLUS中执行时返回却为 1
SQLPLUS脚本：
select count(*)
from serv_acct
where (eff_date = (select max(eff_date) from serv_acct where serv_id = 424858 and acct_item_type_id = 'A21')) and
(serv_id = 424858 and acct_item_type_id = 'A21');

调试很久没有结果，请大侠执教

[beckhambobo]

serv_id = SERV_ID and acct_item_type_id = ACCT_ITEM_TYPE_ID --这样等式相当于完全成立，即全部记录也取出来了。
修改如下：

v_SERV_ID:= 424858;
v_ACCT_ITEM_TYPE_ID := 'A21';

select count(*)
into a
ORDER_SERIAL_NBR
from serv_acct
where (eff_date = (select max(eff_date) from serv_acct where serv_id = v_SERV_ID and acct_item_type_id = v_ACCT_ITEM_TYPE_ID)) and
(serv_id = v_SERV_ID and acct_item_type_id = v_ACCT_ITEM_TYPE_ID);