if object_id('[a]') is not null drop table [a]
go
create table [a]([date] int,[mno] int,[time] int)
insert [a]
select 120601,1,20 union all
select 120602,1,30
go
if object_id('[b]') is not null drop table [b]
go
create table [b]([mno] int,[desp] varchar(3))
insert [b]
select 1,'lwl' union all
select 2,'sp'
go

select a.date,b.mno,b.desp,isnull(time,0) as time
from (select distinct date from a) a
join b on 1=1
left join a as c on c.mno=b.mno and a.date=c.date

/**
date        mno         desp time
----------- ----------- ---- -----------
120601      1           lwl  20
120601      2           sp   0
120602      1           lwl  30
120602      2           sp   0

(4 行受影响)
**/