游标应用在下拉列表时的问题！

[岁月明灯]

以下代码执行后，发现列表框内总是出现一条重复的记录，请教这是什么原因？比如应该显示A、B但下拉列表框内却出现了A、B、B
//ddplb_1赋值
string dd_1
DECLARE help_1 CURSOR FOR
SELECT service_name FROM service_client WHERE client_no=:s_0;
OPEN help_1;
DO While SQLCA.SQLCode=0
FETCH help_1 INTO :dd_1;
ddplb_1.AddItem(dd_1)
Loop
CLOSE help_1;

[-狙击手-]

//ddplb_1赋值
string dd_1
DECLARE help_1 CURSOR FOR
SELECT service_name FROM service_client WHERE client_no=:s_0;
OPEN help_1;
FETCH help_1 INTO :dd_1;
DO While SQLCA.SQLCode=0

ddplb_1.AddItem(dd_1)
FETCH help_1 INTO :dd_1;
Loop
CLOSE help_1;

[岁月明灯]

感谢！强！！！