MCQs

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Overall MCQs for Reference

Which SQL JOIN returns only rows with matching values in both tables?
a. LEFT JOIN
b. RIGHT JOIN
c. INNER JOIN
d. FULL JOIN
Answer: c. INNER JOINdatacamp+2
What is the result of a SQL LEFT JOIN?
a. All rows from the right table
b. Only matching rows
c. All rows from the left table and matching right table rows
d. All unmatched rows only
Answer: c. All rows from the left table and matching right table rowsgeeksforgeeks+1
Which JOIN type produces a Cartesian product of two tables?
a. INNER JOIN
b. LEFT JOIN
c. CROSS JOIN
d. NATURAL JOIN
Answer: c. CROSS JOINkdnuggets+1
What does a FULL OUTER JOIN return?
a. Only matched rows
b. All rows from both tables, matched and unmatched
c. Only unmatched rows
d. All rows from the right table
Answer: b. All rows from both tables, matched and unmatcheddatacamp+1
Which JOIN automatically matches columns with the same name and data type?
a. LEFT JOIN
b. NATURAL JOIN
c. SELF JOIN
d. CROSS JOIN
Answer: b. NATURAL JOINscholarhat+1
In which scenario would you use a SELF JOIN?
a. Comparing rows in different tables
b. Combining unrelated datasets
c. Comparing rows within the same table
d. Returning unmatched rows only
Answer: c. Comparing rows within the same tablegeeksforgeeks+1
Which JOIN includes all rows from the right table even if there is no match in the left table?
a. INNER JOIN
b. LEFT JOIN
c. FULL JOIN
d. RIGHT JOIN
Answer: d. RIGHT JOINdatacamp+1
Given tables Employee and Department, which query shows employee names with their department names using a JOIN?
a. SELECT Emp_name, Dept_name FROM Employee LEFT JOIN Department;
b. SELECT Emp_name, Dept_name FROM Employee NATURAL JOIN Department;
c. SELECT Emp_name FROM Employee;
d. SELECT Dept_name FROM Department;
Answer: b. SELECT Emp_name, Dept_name FROM Employee NATURAL JOIN Department;scholarhat+1
What is a bridging table used for in data joins?
a. Storing temporary data
b. Connecting tables in many-to-many relationships
c. Only joining one-to-one tables
d. Data formatting
Answer: b. Connecting tables in many-to-many relationshipsinterviewbit+1
Which clause is frequently used to specify join conditions?
a. GROUP BY
b. WHERE
c. ON
d. HAVING
Answer: c. ONmode+1
What is the result if there are no matches in an INNER JOIN?
a. NULL records
b. All records returned
c. Empty result set
d. All records from left table
Answer: c. Empty result setgeeksforgeeks+1
What happens to unmatched left table rows in a LEFT JOIN?
a. Removed from output
b. Returned with NULLs for right table columns
c. Returned as empty rows
d. Excluded from the result
Answer: b. Returned with NULLs for right table columnsdatacamp+1
Which SQL JOIN is best for matching student enrollments to courses?
a. RIGHT JOIN
b. CROSS JOIN
c. INNER JOIN
d. FULL JOIN
Answer: c. INNER JOINinterviewbit+1
What does a NATURAL JOIN not require that an INNER JOIN does?
a. Columns with the same name in both tables
b. Explicit join condition
c. Matching rows
d. SELECT statement
Answer: b. Explicit join conditionscholarhat+1
How many tables can be joined in a SQL statement?
a. Only 2 tables
b. Up to 3 tables
c. Unlimited
d. Maximum of 5
Answer: c. Unlimitedmode+1
What key concept enables JOIN operation between tables?
a. Primary key
b. Foreign key
c. Both primary and foreign keys
d. Data types only
Answer: c. Both primary and foreign keysw3schools+1
Which join type may return duplicate columns in the result?
a. NATURAL JOIN
b. CROSS JOIN
c. LEFT JOIN
d. INNER JOIN
Answer: d. INNER JOINinterviewbit+1
Which join operation is suitable for analyzing hierarchical relationships?
a. SELF JOIN
b. NATURAL JOIN
c. RIGHT JOIN
d. FULL JOIN
Answer: a. SELF JOINgeeksforgeeks+1
What does the SQL statement “SELECT * FROM A, B WHERE A.id = B.id;” perform?
a. CROSS JOIN
b. NATURAL JOIN
c. INNER JOIN
d. FULL JOIN
Answer: c. INNER JOINinterviewbit+1
Which scenario is best for using a FULL OUTER JOIN?
a. When unmatched data from both tables is needed
b. Only matched rows required
c. When connecting unrelated data
d. When filtering specific values
Answer: a. When unmatched data from both tables is neededdatacamp+1
Which JOIN technique can you use to join three tables?
a. Multiple INNER JOINs
b. Single LEFT JOIN
c. Only CROSS JOIN
d. Only NATURAL JOIN
Answer: a. Multiple INNER JOINsdataquest+1
For database normalization, many-to-many relationships use:
a. Lookup table
b. Bridging table
c. View table
d. Index table
Answer: b. Bridging tableinterviewbit+1
What is an equi join?
a. Join on equality of columns
b. Join disregarding conditions
c. Join with all columns
d. Join on aggregate values
Answer: a. Join on equality of columnsgeeksforgeeks+1
Which JOIN would you use to bring all rows from two tables where there’s any matching value?
a. LEFT JOIN
b. FULL OUTER JOIN
c. SELF JOIN
d. NATURAL JOIN
Answer: b. FULL OUTER JOINdatacamp+1
Which SQL JOIN fetches all possible combinations of two tables?
a. CROSS JOIN
b. LEFT JOIN
c. RIGHT JOIN
d. INNER JOIN
Answer: a. CROSS JOINkdnuggets+1
What is the main use of INNER JOIN?
a. Retrieve unrelated data
b. Retrieve related data based on matching values
c. Retrieve all unmatched data
d. Retrieve single table records
Answer: b. Retrieve related data based on matching valueskdnuggets+1
Which clause can filter joined rows after joining?
a. WHERE
b. HAVING
c. ON
d. GROUP BY
Answer: a. WHEREmode+1
A join where the same table is joined with itself is called:
a. NATURAL JOIN
b. SELF JOIN
c. CROSS JOIN
d. LEFT JOIN
Answer: b. SELF JOINgeeksforgeeks+1
Which JOIN type will return all records from one table even if there are no matches in another table?
a. INNER JOIN
b. NATURAL JOIN
c. LEFT JOIN
d. CROSS JOIN
Answer: c. LEFT JOINdatacamp+1
What will be the output if no matching columns exist in a NATURAL JOIN?
a. Error
b. All rows from both tables
c. Empty set
d. NULL values only
Answer: c. Empty setscholarhat+1
Which operator is typically used for joining tables in SQL?
a. +
b. ON
c. ||
d. *
Answer: b. ONmode+1
What would you use to combine customer records with their orders?
a. INNER JOIN on customer and order tables
b. FULL JOIN on orders
c. NATURAL JOIN on unrelated columns
d. CROSS JOIN only
Answer: a. INNER JOIN on customer and order tableskdnuggets+1
Which JOIN includes all possible combinations of two tables regardless of relationships?
a. INNER JOIN
b. CROSS JOIN
c. FULL JOIN
d. NATURAL JOIN
Answer: b. CROSS JOINgeeksforgeeks+1
Which SQL JOIN is best for showing salary details for employees regardless of whether salary is recorded?
a. LEFT JOIN
b. INNER JOIN
c. NATURAL JOIN
d. SELF JOIN
Answer: a. LEFT JOINdatacamp+1
Which JOIN returns only rows where a condition matches in both tables?
a. RIGHT JOIN
b. FULL OUTER JOIN
c. INNER JOIN
d. LEFT OUTER JOIN
Answer: c. INNER JOINkdnuggets+1
What join type should be used for exploratory combinatorial data analysis?
a. CROSS JOIN
b. SELF JOIN
c. LEFT JOIN
d. FULL JOIN
Answer: a. CROSS JOINkdnuggets+1
Which type of JOIN helps analyze organizational hierarchy data in a single table?
a. NATURAL JOIN
b. SELF JOIN
c. CROSS JOIN
d. FULL JOIN
Answer: b. SELF JOINgeeksforgeeks+1
When joining multiple tables, each JOIN statement must have:
a. Faster index
b. An appropriate condition
c. More columns
d. Aggregation
Answer: b. An appropriate conditionscholarhat+1
What type of join will yield all students paired with all subjects, regardless of enrollment?
a. INNER JOIN
b. CROSS JOIN
c. LEFT JOIN
d. NATURAL JOIN
Answer: b. CROSS JOINkdnuggets+1
Which JOIN would you use for retrieving all instructors even if some courses have no instructor assigned?
a. RIGHT JOIN
b. NATURAL JOIN
c. INNER JOIN
d. SELF JOIN
Answer: a. RIGHT JOINscholarhat+1
The result of joining multiple tables using INNER JOIN will be:
a. All rows from all tables
b. Only matching rows based on join conditions
c. Only unmatched rows
d. NULL for non-matching values
Answer: b. Only matching rows based on join conditionsscholarhat+1
In SQL, the JOIN keyword is synonymous with:
a. RIGHT JOIN
b. INNER JOIN
c. LEFT JOIN
d. CROSS JOIN
Answer: b. INNER JOINdatacamp+1
SQL JOIN clause is mainly used for:
a. Indexing tables
b. Combining rows from multiple tables
c. Filtering rows before grouping
d. Aggregating values
Answer: b. Combining rows from multiple tablesw3schools+1
To find employees not assigned to any department, which JOIN type is useful?
a. LEFT JOIN combined with WHERE department IS NULL
b. FULL JOIN only
c. NATURAL JOIN
d. INNER JOIN only
Answer: a. LEFT JOIN combined with WHERE department IS NULLcoursera+1
The result of “SELECT * FROM TableA CROSS JOIN TableB” is:
a. Only matched rows
b. Cartesian product
c. Outer join
d. Inner join
Answer: b. Cartesian productkdnuggets+1
What is an OUTER JOIN?
a. Join returning only matched rows
b. Join including unmatched rows from one or both tables
c. Join selecting single rows only
d. Join with no condition
Answer: b. Join including unmatched rows from one or both tablescoursera+1
Which JOIN can introduce NULL values for missing matched data?
a. CROSS JOIN
b. LEFT JOIN
c. INNER JOIN
d. SELF JOIN
Answer: b. LEFT JOINcoursera+1
SQL joins can be performed between tables if they have:
a. Related columns
b. Different data types only
c. No columns in common
d. Only numeric columns
Answer: a. Related columnsw3schools+1
What does a NATURAL JOIN return if more than one pair of columns match by name and type?
a. Only one column per pair, eliminating duplicates
b. All columns from both tables
c. NULL values only
d. Nothing
Answer: a. Only one column per pair, eliminating duplicatesscholarhat+1
A JOIN in SQL is ideal for:
a. Combining result sets from multiple queries
b. Combining rows from tables based on logic
c. Printing tables only
d. Updating values
Answer: b. Combining rows from tables based on logicdataquest+1

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