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create table t1 ( id int not null, planet varchar(20) not null ) ;
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insert into t1 (id, planet) values (1, 'jupiter');
1 rows affected
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insert into t1 (id, planet) values (2, 'earth');
1 rows affected
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create table t2 ( id int not null, planet varchar(20) not null ) ;
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insert into t2 (id, planet) values (1, 'jupiter');
1 rows affected
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insert into t2 (id, planet) values (2, 'earth');
1 rows affected
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SELECT * FROM t1 NATURAL JOIN t1;
ID PLANET
1 jupiter
1 jupiter
2 earth
2 earth
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SELECT id, planet FROM t1 NATURAL JOIN t1 t2;
ID PLANET
1 jupiter
2 earth
 hidden batch(es)


SELECT * FROM t1 NATURAL JOIN t2;
ID PLANET
1 jupiter
2 earth
 hidden batch(es)


SELECT id, planet FROM t1, t1;
ORA-00918: column ambiguously defined
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SELECT id, planet FROM t1, t2 t1;
ORA-00918: column ambiguously defined
 hidden batch(es)