var
   j:string;
begin
   j:='Select JH,SJRQ From SGGZ Where gxsjwc is null And (ysjbz=''Y'' or ysjbz is Null) And cjdwdm='''+edtCJDWDM.Text+''' Order by SJRQ Desc' ;
   ado.sql.clear;
   ado.sql.add(j);
   ado.open();
end;

将下面的SQL在PL/SQL中执行一下，看是不是通过的
Select JH, SJRQ
  From SGGZ
 Where gxsjwc is null
   And (ysjbz = 'Y' or ysjbz is Null)
   And cjdwdm = 'edtCJDWDM'
 Order by SJRQ Desc

------解决方案--------------------
"Select JH,SJRQ From SGGZ Where gxsjwc is null And (ysjbz='Y' or ysjbz is Null) And cjdwdm='''+edtCJDWDM.Text+''' Order by SJRQ Desc"


------解决方案--------------------
单引号和双引号都有问题，
"Select JH,SJRQ From SGGZ Where gxsjwc is null And (ysjbz='Y' or ysjbz is Null) And cjdwdm='"+edtCJDWDM.Text+"' Order by JH"

------解决方案--------------------
ysjbz=''Y'' or ysjbz is Null
这个也可以这样
nvl(ysjbz,'Y')='Y'
主要看你报什么错误

------解决方案--------------------
我在delphi看了你的SQL,字符串组成没有问题，
如下：
Select JH,SJRQ From SGGZ Where gxsjwc is null And (ysjbz='Y' or ysjbz is Null) And cjdwdm='aa' Order by JH

可能是你delphi的ADO连接用户权限问题吧，
或者你的adodataset连接问题；


------解决方案--------------------
贴出Delphi代码来

------解决方案--------------------
探讨

Select JH,SJRQ,SQRQ,cjdwdm From SGGZ Where gxsjwc is null And (ysjbz='Y' or ysjbz is Null) Order by JH 
PL/SQL 里面是可以运行得出正确结果的。 
但是程序里面没结果呀。