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Choose three.

Which three statements are true about a self join?

A) It must be an inner join.

B) It can be an outer join.

C) The ON clause must be used.

D) It must be an equijoin.

E) The query must use twodifferent aliases for the table.

F) The ON clause can be used.

Answer::BCD

(parsing: the left join is actually the left outer connection, it's just a different name, and the result is the same. ANSI grammar has the syntax of left join, while oracle grammar uses (+) to express.

Select emp.empno,emp.deptno,dept.deptno,dept.dname

From emp left join dept on emp.deptno=dept.deptno

Select emp.empno,emp.deptno,dept.deptno,dept.dname

From emp left outer join dept on emp.deptno=dept.deptno

Select emp.empno,emp.deptno,dept.deptno,dept.dname

From emp, dept

Where emp.deptno=dept.deptno (+)

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