Do Left or Inner Join depends on parameter

I have to do 'left' or 'inner' join operation between tables depends on input parameter in my stored procedure. I know how to 开发者_如何转开发do it very simply:

if flag = 0
begin 
 select t1.*, t2.* from t1 
 inner join t2 on t2.id=t1.id 
end
else 
begin
 select t1.*, t2.* from t1 
 left join t2 on t2.id=t1.id 
end 

Is there any more solution ? Thank you

you can do it using only left join by doing something like this

select t1.*, t2.* from t1 
 left outer join t2 on t2.id=t1.id 
WHERE flag = 1 OR t2.id IS NOT NULL

You didn't mention the language, so maybe something like this:

select t1.*, t2.* from t1 
left join t2 on t2.id=t1.id 

if flag = 0
begin 
 where t2.id is not null
end

 select t1.*, t2.* 
   from t1 
        inner join t2 on t2.id = t1.id 
  where flag = 0
 UNION
 select t1.*, t2.* 
   from t1 
        left outer join t2 on t2.id = t1.id
  where coalesce(flag, 1) <> 0;