SQL Self Join
6.What does this return?- If Ravi is a top-level manager?
SELECT A.name, B.name
FROM employees A
LEFT JOIN employees B ON A.manager_id = B.id;
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A. NULL in B.name for Ravi
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B. Skips Ravi
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C. Ravi joins with himself
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D. Error
NULL in B.name for Ravi
NULL in B.name for Ravi
7.Which scenario suits SELF JOIN best?
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A. Products with categories
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B. Employee hierarchy
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C. Courses and students
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D. Normalization
Employee hierarchy
Employee hierarchy
8.Output of this query: If e1 has no manager, then manager column = ?
SELECT e1.name, e2.name AS manager
FROM employees e1
LEFT JOIN employees e2 ON e1.manager_id = e2.id;
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A. e1.name
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B. NULL
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C. 0
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D. Error
NULL
NULL
9.In a SELF JOIN, how many copies of the same table are used in FROM clause?
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A. 1
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B. 2
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C. Unlimited
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D. Depends on data
2
2
10.Can aliases be used in SELF JOIN?
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A. No
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B. Yes, required
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C. Optional
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D. Aliases not supported in SQL
Yes, required
Yes, required