Oracle not exsits select 1

exsits内で使用する「select 1」は「select *」と内容的には同じ
 
 

■testテーブルとtest2テーブルを用意

・select * from test;

id	name
1	tanaka
2	nakagawa
3	yoshida

 
 
・select * from test2;

id	age
1	20
2	30
3	40

 
 

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■select結果

・select * from test t1, test2 t2
where not exists (select 1 from test2 where t1.id = t2.id and t2.id = 2);

id	name	id_1	age
1	tanaka	1	20
1	tanaka	2	30
1	tanaka	3	40
2	nakagawa	1	20
2	nakagawa	3	40
3	yoshida	1	20
3	yoshida	2	30
3	yoshida	3	40

 
 
・select count(1) from test t1, test2 t2
where not exists (select 1 from test2 where t1.id = t2.id and t2.id = 2);

count(1)
8