PostgreSQL的：選擇特定的列及其總行數

Question

我會解釋我的問題與樣品例如

create table foo(id int,idx int,idy int,fld int,fldx varchar); 

insert into foo values (1,2,3,55,'AA'),(2,3,4,77,'AB'),(3,4,8,55,'AX'),(9,10,15,77,'AR'), 
         (3,4,8,11,'AX'),(3,4,8,65,'AX'),(3,4,8,77,'AX'); 




    id,idx,idy, fld,fldx 
    1 2 3 55 AA 
    2 3 4 77 AB 
    3 4 8 55 AX 
    9 10 15 77 AR 
    3 4 8 11 AX 
    3 4 8 65 AX 
    3 4 8 77 AX 

，我需要選擇只列fld以降序

其每列（ fld）的總數

預期結果：

fld count 
--------- 
77 3 
55 2 
11 1 
65 1 

Answer 1

select fld 
     ,count(fld) rw_count 
from foo 
group by fld 
order by rw_count desc 

Group By

Answer 2

select fld,count(*) from foo group by 1 order by 2 desc ;