MSSQL Count function on a small example of

- Create Test Table 
IF  object_id (N ' T_Test ' , N ' the U- ' ) IS  null      
  the CREATE  TABLE  [ the dbo ] . [ T_Test ] (
   [ ID ]  int  the IDENTITY ( . 1 , . 1 ) a PRIMARY  Key  the NOT  NULL ,
   [ Grouping ]  VARCHAR ( 50 ) the NOT  NULL ,
   [ Ret ]   varchar(10) null,
  [Chk]   varchar(10) NULL
  )
GO
--插入数据
insert into T_Test values('A', 1, 'XXX')
insert into T_Test values('A', 2, 'XXX')
insert into T_Test values('A', 2, 'YYY')
insert into T_Test values('A', 2, null )
insert into T_Test values('A', 2, '' )
insert into T_Test values('A', null, 'cc' )
insert into T_Test values('A', '', 'cc' )
insert into T_Test values('B', 1, 'YYY')
insert into T_Test values('B', 3, 'XXX')
insert into T_Test values('B', 2, 'XXX')
insert into T_Test values('B', 4, null )
insert into T_Test values('B', 5, '' )
insert into T_Test values('B', null, 'cc' )
insert into T_Test values('B', '', ' CC ' ) 

- . 1, according to the field of the packet Grouping Statistics field Ret (not empty) the number of different values, 
- 2. Grouping the chk field of the packet is not empty, Statistics field Ret (not empty) different the number of values, 
- using mainly functions do not count the number of statistical nULL, nullif function 
SELECT  GROUPING , 
        - count (DISTINCT Case When ISNULL (RET, '') <> '' End null the else the then RET), 
       count ( DISTINCT  NULLIF ( RET, '' )),
        COUNT ( DISTINCT  Case  When  ISNULL (CHK, '' ) <> ''  the then  NULLIF (RET, '') Else  zero end)
from t_test group by GROUPING
MSSQL Count function on a small example of

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