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    Question

    In SQL, which type of join returns all records from the

    left table and the matched records from the right table, and fills in NULL values for non-matching records in the right table?
    A INNER JOIN Correct Answer Incorrect Answer
    B RIGHT JOIN Correct Answer Incorrect Answer
    C FULL OUTER JOIN Correct Answer Incorrect Answer
    D LEFT JOIN Correct Answer Incorrect Answer
    E CROSS JOIN Correct Answer Incorrect Answer

    Solution

    The "LEFT JOIN" in SQL is a type of join operation that returns all rows from the left table and the matched rows from the right table, placing NULL in columns from the right table where there is no match. This type of join is useful when analyzing data where you want to retain all records from the primary dataset (left table) but only include matching data from the auxiliary dataset (right table). For instance, if querying a customer database with order information, a LEFT JOIN ensures all customers are shown even if they have no orders. This join type supports robust reporting as it ensures data completeness from the main table. Option A (INNER JOIN) is incorrect as it only returns rows with matches in both tables. Option B (RIGHT JOIN) is incorrect because it includes all rows from the right table, not the left. Option C (FULL OUTER JOIN) is incorrect because it includes all records from both tables, filling NULLs where there’s no match. Option E (CROSS JOIN) is incorrect as it returns the Cartesian product of the tables, not a matched set.

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