EXERCISE 14 PART 2
8) EXISTS takes a value of false if the subquery returns an intermediate result set.
FALSE
1) Using an outer join produces this information: rows that do not have matching values in common columns are not included in the result table.
FALSE
10) A subquery in which processing the inner query depends on data from the outer query is called a codependent query.
FALSE
13) Subqueries can only be used in the WHERE clause.
FALSE
15) IF-THEN-ELSE logical processing cannot be accomplished within an SQL statement.
FALSE
17) It is better not to have a result set identified before writing GROUP BY and HAVING clauses for a query.
FALSE
18) Specifying the attribute names in the SELECT statement will make it easier to find errors in queries and also correct for problems that may occur in the base system.
FALSE
2) One major disadvantage of the outer join is that information is easily lost.
FALSE
20) Combining a table with itself results in a faster query.
FALSE
22) Transaction integrity commands are not used to identify whole units of database changes that must be completed in full for the database to retain integrity.
FALSE
24) DBA_USERS contains comments on all tables in an Oracle database.
FALSE
3) There is a special operation in SQL to join a table to itself.
FALSE
6) The following query will execute without errors. select customer.customer_name, salesman.sales_quota from customer where customer.salesman_id = (select salesman_id where lname = 'SMITH');
FALSE
11) The following SQL statement is an example of a correlated subquery. select first_name, last_name, total_sales from salesman s1 where total_sales > all (select total_sales from salesman s2 where s1.salesman_id != s2.salesman_id);
TRUE
12) A correlated subquery is executed once for each iteration through the outer loop.
TRUE
14) The UNION clause is used to combine the output from multiple queries into a single result table.
TRUE
16) Figuring out what attributes you want in your query before you write the query will help with query writing.
TRUE
19) Correlated subqueries are less efficient than queries that do not use nesting.
TRUE
21) A transaction is the complete set of closely related update commands that must all be done, or none of them done, for the database to remain valid.
TRUE
23) RDBMSs store database definition information in system-created tables which can be considered a data dictionary.
TRUE
25) SQL:2008 allows one to calculate linear regressions, moving averages and correlations without moving the data outside of the database.
TRUE
4) Joining tables or using a subquery may produce the same result.
TRUE
5) The following queries produce the same results. select customer_name, customer_city from customer, salesman where customer.salesman_id = salesman.salesman_id and salesman.lname = 'SMITH'; select customer_name, customer_city from customer where customer.salesman_id = (select salesman_id from salesman where lname = 'SMITH')
TRUE
7) In order to find out what customers have not placed an order for a particular item, one might use the NOT qualifier along with the IN qualifier.
TRUE
9) When EXISTS or NOT EXISTS is used in a subquery, the select list of the subquery will usually just select all columns as a placeholder because it doesn't matter which columns are returned.
TRUE