復制代碼 代碼如下:

if (object_id ('t_test' )> 0 )
drop table t_test
go
create table t_test (a sql_variant , b sql_variant , c sql_variant )
insert into t_test select 1 , 1 , 'a'
insert into t_test select 1 , getdate (), null
insert into t_test select 'a' , null , 1
insert into t_test select 3 , null , null
insert into t_test select null , null , null
go
select * from t_test
go
select
count (* )--總數
, count (nullif (1 , 1 ))--永遠返回0
, count (a )--a數量
, count (b)--b數量
, count (distinct a )--a不重復數量
, count (isnull (b, c ))--b或者c不為null數量
, count (Coalesce (a , b, c )) --a或者b或者c不為null數量
, count (nullif (a , b))--a不等于b的數量
, count (nullif (isnumeric (cast (a as varchar (38 ))), 0 ))--a是數字的數量
from t_test