在兩列中選擇不同的計數

Question

我有看起來像這樣的數據：

school       district        crs_sbj  crs_num  crs_sec
CANYON HIGH  IRON DISTRICT   ENGL     2010     213
CANYON HIGH  IRON DISTRICT   ENGL     2010     214
CANYON HIGH  IRON DISTRICT   ENGL     1010     110
CANYON HIGH  IRON DISTRICT   MATH     1010     400
WAYNE HIGH   WAYNE DISTRICT  MATH     1010     321
WAYNE HIGH   WAYNE DISTRICT  MATH     1010     322
WAYNE HIGH   WAYNE DISTRICT  ENGL     1010     500

我想計算每所高中提供的獨特課程。 例如，我想看：

   count   school
    3       CANYON HIGH
    2       WAYNE HIGH

我將如何去做呢？ 我了解一欄的概念，但是兩欄呢？

Answer 1

嘗試這個：

select school, count(distinct crs_num) _count
from table 
group by school;

Answer 2

Select School, count(distinct crs_num)
from  table
group by School

Answer 3

我不確定什么是獨特的課程。

; with aardvark (select distinct school, district, crs_sbj, crs_num
    from T)
select district, school, count(*)
from aardvark
group by school, district

由於可以在各地區使用相同的學校名稱，因此我將地區包括在分組中。