declare @t table(a nvarchar(20),b nvarchar(20))

insert into @t values('a','a')
insert into @t values('a','b')
insert into @t values('a','c')
insert into @t values('d','d')
insert into @t values('a','e')

SELECT * FROM @t WHERE a<>'a' AND b<>'a'
/*
a                    b
-------------------- --------------------
d                    d
*/
SELECT * FROM @t WHERE a+b<>'aa'
/*
a                    b
-------------------- --------------------
a                    b
a                    c
d                    d
a                    e
*/

------解决方案--------------------
SQL code
declare @t table(a nvarchar(20),b nvarchar(20))

insert into @t values('a','a')
insert into @t values('a','b')
insert into @t values('a','c')
insert into @t values('d','d')
insert into @t values('a','e')

select * from @t where a <> 'a' or b <> 'a'

/*
a                    b                    
-------------------- -------------------- 
a                    b
a                    c
d                    d
a                    e

（所影响的行数为 4 行）
*/