sql - can we replace full join with union of left and right join? why not? -

can replace full join union of left , right join? if no,why?

'yes' if t1 , t2 sets (no duplicated rows), otherwise answer 'no'.

create table t1 (i int); create table t2 (i int);  insert t1 values (1); insert t1 values (2); insert t1 values (2);  insert t2 values (3); 

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full join

select * t1 full join t2 on t1.i=t2.i  order 1,2 

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1   (null) 2   2 2   2 (null)  3 

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union

select * t1 left join  t2 on t1.i=t2.i union select * t1 right join t2 on t1.i=t2.i order 1,2 

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1   (null) 2   2 (null)  3   

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union all

select * t1 left join  t2 on t1.i=t2.i union select * t1 right join t2 on t1.i=t2.i order 1,2 

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1   (null) 2   2 2   2 2   2 2   2 (null)  3