Question

SELECT Country.Code, Country.Name

FROM Country

WHERE Country.Code NOT IN( SELECT CountryCode FROM CountryLanguage );

In the above query the statement SELECT CountryCode FROM CountryLanguage

is a:

a) Sub query

b) UNION Statement

c) NATURAL JOIN

d) INNER JOIN

Answer 1

The statement 'SELECT CountryCode FROM CountryLanguage' is a sub query in the above query.

Step-by-step explanation:

The statement 'SELECT CountryCode FROM CountryLanguage' is a sub query in the above query. A sub query is a query nested within another query. In this case, the sub query is used to retrieve the 'CountryCode' from the 'CountryLanguage' table. The main query then uses the result of the sub query to exclude those country codes from the 'Country' table

Answer 2

The statement "SELECT CountryCode FROM CountryLanguage" in the query is a subquery. Option a is correct.

Step-by-step explanation:

In SQL, a subquery is a query nested within another query, allowing for more complex and specific data retrieval. In this case, the subquery is used within the NOT IN clause to find Country Codes that do not exist in the CountryLanguage table. The main query selects Country Codes and Names from the Country table where the Country Code does not have a match in the CountryLanguage table, essentially retrieving countries where the language information is not present in the CountryLanguage table. Subqueries are powerful tools in SQL, enabling the combination of multiple conditions or criteria for data extraction or manipulation.

The correct answer is: a) Subquery