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Say I have two tables and they have some attributes in common, assume x is common, now will x will appear once in the output or twice for following cases?

Natural join

Cross product

Conditional join

### 1 comment

Once in natural join and twice in others

$R$

 A B 1 2 1 3 2 1

$S$

 A C 1 3 2 3 2 4

Case I) $R\Join S$

 A B C 1 2 3 1 3 3 2 1 3 2 1 4

Case II) $R\times S$

 A B A C 1 2 1 3 1 2 2 3 1 2 2 4 1 3 1 3 1 3 2 3 1 3 2 4 2 1 1 3 2 1 2 3 2 1 2 4

Case III) $R\Join _{A>1 } S$

 A B A C 2 1 1 3 2 1 2 3 2 1 2 4

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