SQL and Database Management MCQs

What is the purpose of the SQL command `ALTER TABLE`?

• To create a new table

• To delete an existing table

• To modify the structure of an existing table

• To retrieve data from a table

Which SQL command is used to remove all records from a table without deleting the table itself?

• DROP TABLE

• DELETE TABLE

• TRUNCATE TABLE

• REMOVE TABLE

What is the function of the `GROUP BY` clause in SQL?

• To filter records

• To sort records

• To group rows that have the same values into summary rows

• To update records

How would you find the number of rows in a table named `Employee`?

• SELECT TOTAL(ROW) FROM Employee;

• SELECT COUNT(*) FROM Employee;

• SELECT NUM_ROWS FROM Employee;

• SELECT ROW_COUNT() FROM Employee;

Which SQL clause is used to restrict the number of rows returned by a query?

• LIMIT

• WHERE

• HAVING

• TOP

What is the default sorting order of the `ORDER BY` clause in SQL?

• Descending

• Ascending

• Random

• By primary key

In SQL, which command would you use to remove a column from a table?

• REMOVE COLUMN

• DROP COLUMN

• DELETE COLUMN

• ALTER COLUMN

Which SQL function is used to calculate the total sum of a numeric column?

• TOTAL()

• SUM()

• ADD()

• COUNT()

What does the SQL `DISTINCT` keyword do in a query?

• It returns unique values

• It orders the results

• It deletes duplicate rows

• It updates the table

Which constraint ensures that a column cannot have a NULL value?

• UNIQUE

• DEFAULT

• PRIMARY KEY

• NOT NULL