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’ , nu
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 (* )–总数
, count (nullif (1 , 1 ))–永远返回0
, count (a )–a数量
, count (b)–b数量
, count (distinct a )–a不重复数量
, count (isnull (b, c ))–b或者c不为null数量
, count (Coalesce (a , b, c )) –a或者b或者c不为null数量
, count (nullif (a , b))–a不等于b的数量
,本文来源gaodaimacom搞#代%码@网- count (nullif (isnumeric (cast (a as varchar (38 ))), 0 ))–a是数字的数量
from t_test
，
转载请注明原文链接：解析关于SQL语句Count的一点细节
