请教一个统计问题
ADOQuery.SQL.Add('select count(ID) as C1,'+
'(select count(DQZK) from [TB1] where DQZK is not null) as C2,'+
'(select count(DQZK) from [TB1] where DQZK is null) as C3'+
'from [TB1] ');
ADOQuery.Open;

DQZK字段里，有些是空白没有内容的。

希望查询能分别得到

总数量、DQZK空白的数量、DQZK不是空白的数量
[解决办法]

--测试数据 mssql2000
create table TB1(id int, DQZK varchar(10));
go

insert into TB1 select 1, null; 
insert into TB1 select 2, 'abc'; 
insert into TB1 select 3, null; 
insert into TB1 select 4, 'dd'; 
insert into TB1 select 5, 'dv';
go

--测试代码
select C1 = sum(a) + sum(b), C2 = sum(a), C3 = sum(b) 
from(
select a = case when dqzk is null then sum(1)end,
b = case when dqzk is not null then sum(1) end
from tb1 group by dqzk) a