Advanced SQL Quiz

What does the `IS NULL` operator do in SQL?

• Checks if a value is not NULL.

• Checks if a value is NULL.

• Assigns a NULL value to a column.

• Removes NULL values from a result set.

In SQL, what is a foreign key?

• A key that uniquely identifies each row within its own table.

• A key used to link two tables together.

• A key that can only contain unique values.

• A key used to speed up searches.

Which SQL keyword is used to fetch the current date and time?

• CURRENT_DATE()

• GETDATE()

• NOW()

• TODAY()

What does the `AND` operator do in SQL?

• Combines multiple columns.

• Combines multiple conditions.

• Sorts data in ascending order.

• Filters data.

Which SQL function is used to count the number of rows in a table?

• COUNT()

• SUM()

• TOTAL()

• CALCULATE()

In SQL, what is the difference between `INNER JOIN` and `OUTER JOIN`?

• `INNER JOIN` selects matching rows; `OUTER JOIN` selects all rows with matches.

• `INNER JOIN` selects all rows; `OUTER JOIN` selects matching rows only.

• `INNER JOIN` selects rows with matches in both tables; `OUTER JOIN` includes non-matching rows.

• `INNER JOIN` selects rows with NULL values; `OUTER JOIN` excludes NULL values.

Identify the SQL function that returns the current date and time.

• NOW()

• DATE()

• TIME()

• CURRENT()

Which SQL keyword is used to retrieve unique records?

• SELECT DISTINCT

• SELECT UNIQUE

• SELECT DISTINCTIVE

• SELECT DIFFERENT

Identify the function used to calculate the sum of values in a numeric column.

• SUM()

• COUNT()

• AVG()

• MAX()

Which SQL command is used to add a column to an existing table?

• MODIFY TABLE table_name ADD column_name datatype;

• ALTER TABLE table_name ADD column_name datatype;

• UPDATE TABLE table_name ADD column_name datatype;

• CHANGE TABLE table_name ADD column_name datatype;