DBMS_2

Which of the following is a valid DDL command?

• SELECT

• INSERT

• DROP

• UPDATE

What does the NOT NULL constraint ensure?

• Column must have unique values

• Column must have non-null values

• Column must be primary key

• Column cannot be indexed

Which clause can be used with GROUP BY to filter aggregate results?

• WHERE

• HAVING

• ORDER BY

• DISTINCT

Which keyword is used to change an existing record in a table?

• UPDATE

• MODIFY

• CHANGE

• SET

Which type of join returns only the matched records from both tables?

• FULL JOIN

• LEFT JOIN

• RIGHT JOIN

• INNER JOIN

What does SELECT COUNT(*) return?

• Number of columns

• Number of tables

• Number of rows

• Number of distinct rows

What does DISTINCT do in a query?

• Removes all nulls

• Sorts the results

• Removes duplicate rows

• Filters rows based on condition

What is the role of a foreign key?

• Makes a column unique

• Links two tables together

• Ensures primary key

• Creates a view

Which clause specifies the sort order in a SELECT statement?

• GROUP BY

• HAVING

• ORDER BY

• SELECT

Which of these joins is symmetrical in behavior?

• LEFT JOIN

• RIGHT JOIN

• FULL OUTER JOIN

• INNER JOIN