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Which join refers to join records from the write table that have no...

  • Q.

    Which join refers to join records from the write table that have no matching key in the left table are include in the result set:

  • filter_dramaExplanation
    Answer is : B

    A right outer join will return all the rows that an inner join returns plus one row for each of the other rows in the second table that did not have a match in the first table. It is the same as a left outer join with the tables specified in the opposite order.

    Outer joins are of following three types.

    1. Left outer join
    2. Right outer join
    3. Full outer join

    Right Outer Join : The right join operation returns all record from right table and matching records from the left table. On a matching element not found in left table, NULL is represented in that case.

     

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Similar Questions

  • 1.

    Which view that contains more than one table in the top-level FROM clause of the SELECT statement:

  • filter_dramaExplanation
    Answer is : C

    The DELETE statement is used to delete rows in a table. The UPDATE statement is used to update existing records in a table. The INSERT INTO statement is used to insert new records in a table.

  • 2.

    Consider the following two tables and four queries in SQL.

    Book (isbn, bname), Stock (isbn, copies)

    Query 1:

    SELECT B.isbn, S.copies
    FROM Book B INNER JOIN Stock S
    ON B.isbn = S.isbn;
    

    Query 2:

    SELECT B.isbn, S.copies
    FROM B B LEFT OUTER JOIN Stock S
    ON B.isbn = S.isbn;

    Query 3:

    SELECT B.isbn, S.copies
    FROM Book B RIGHT OUTER JOIN Stock S
    ON B.isbn = S.isbn;

    Query 4:

    SELECT B.isbn, S.copies
    FROM B B FULL OUTER JOIN Stock S
    ON B.isbn = S.isbn;

    Which one of the queries above is certain to have an output that is a superset of the outputs of the other three queries?

  • filter_dramaExplanation
    Answer is : D

    In SQL the FULL OUTER JOIN combines the results of both left and right outer joins and returns all (matched or unmatched) rows from the tables on both sides of the join clause.

    So, option (D) is correct.

  • 3.

    Given two tables R1(x, y) and R2(y, z) with 50 and 30 number of tuples respectively. Find maximum number of tuples in the output of natural join between tables R1 and R2 i.e. R1 * R2? (*. Natural Join)

  • filter_dramaExplanation
    Answer is : D

    Concept:

    A natural join is based on common attributes or common columns to join two tables or relations.

    Explanation:

    Consider an example, suppose there are two tables Employee(Eid, Ename) consists of 5 tuples and department(Eid, Did) consists of 3 tuples only.

    Eid

    Ename

    1

    E1

    1

    E2

    1

    E3

    1

    E4

    1

    E5

     

    Eid

    Did

    1

    D1

    1

    D2

    1

    D3

     

    Natural join of employee and department(Employee * Department) gives:

    5 × 3 = 15

    So, maximum number of tuples in natural join are from the relation having minimum tuples. So, in given question, R2 contains 30 tuples, so , maximum number of tuples in the output of natural join between tables R1 and R2 i.e. R1 * R2 = 50 × 30 = 1500.

  • 4.

    A condition is referred to as __________

  • filter_dramaExplanation
    Answer is : B

    An SQL join clause combines records from two or more tables in a database. It creates a set that can be saved as a table or used as it is. A JOIN is a means for combining fields from two tables by using values common to each.

  • 5.

    What is Join Operation denoted by?

  • filter_dramaExplanation
    Answer is : D

    Join Operation is denoted by ⋈.

    A JOIN clause is used to combine rows from two or more tables, based on a related column between them.

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