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POinner joins in oracle
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  1. POinner joins in oracle
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    copied!<p>I was thinking about the syntax of inner joins in Oracle's SQL implementation and here is something that seems a bit inconsistent:</p> <p>Let's say you have two relations loan(loan_number, branch_name, amount) and borrower(customer_name, loan_number). loan_number is the attribute common to both tables. Now, Oracle gives you two ways to express an inner join:</p> <pre><code>select * from loan, borrower where loan.loan_number = borrower.loan_number; </code></pre> <p>The above statement is equivalent to:</p> <pre><code>select * from loan inner join borrower on loan.loan_number = borrower.loan_number; </code></pre> <p>However, when expressing a cross join there is only one way to express it:</p> <pre><code>select * from loan, borrower; </code></pre> <p>The following statement is syntactically incorrect:</p> <pre><code>select * from loan inner join borrower; </code></pre> <p>This is invalid; Oracle expects the ON... part of the clause</p> <p>Given that an inner join is just a cross join with a filter condition, do you guys think that this is an inconsistency in Oracle's SQL implementation? Am I missing something? I'd be interested in hearing some other opinions. Thanks.</p> <p>As David pointed out in his answer the syntax is:</p> <pre><code>select * from loan cross join borrower; </code></pre> <p>Even though I was not aware of the above syntax I still think it's inconsistent. Having the cross join keyword in addition to allowing inner join without a join condition would be fine. A cross join is in fact an inner join without a join condition, why not express it as an inner join without the join condition? </p>
 

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