求一条sql语句，在线等.....

Question

有数据表T,如下结构：字段     A                B
         1                2007-01-01
         1                2007-01-01
         1                2007-01-01
         2                2007-01-02
         5                2001-01-02
         6                2001-01-10
         1                2001-01-11要求计算记录的数量，条件是当天A字段重复的统计一次，对于上述记录实际上等效于对下面的结果集进行计数
字段     A                B
         1                2007-01-01
         2                2007-01-02
         5                2001-01-02
         6                2001-01-10
         1                2007-01-11

Answer 1

select distinct A,B
  from T;就这么简单?难道我理解错误?

Answer 2

要求计算记录集中记录数量count(*)

Answer 3

select count(*) from (select distinct A, B from T);是这样的吗?