Oracle Updated 1z0-071 Exam Questions and Answers by stephen

A. True. When using set operators, the number and order of columns must be the same in all SELECT statements involved in the query. The data types of those columns must also be compatible.

E. True. The FOR UPDATE clause cannot be specified in a subquery or a SELECT statement that is combined with another SELECT statement by using a set operator.

B is incorrect because the column names do not need to match; only the number and data types of the columns must be compatible. C is incorrect because only the final SELECT statement in the sequence of UNION/INTERSECT/MINUS operations can have an ORDER BY clause. D is incorrect because, as of Oracle 12c, UNION ALL can be used with CLOB columns, but UNION, INTERSECT, and MINUS cannot.

When the TRUNCATE TABLE command is used:

• C. It retains the indexes defined on the table. This is true. The TRUNCATE TABLE operation does not drop the indexes on the table; it only removes all rows from the table.
• D. It retains the integrity constraints defined on the table. This is correct. The TRUNCATE TABLE operation does not affect the integrity constraints; it retains them.

Options A, B, E, and F are incorrect:

• A is incorrect because the TRUNCATE TABLE operation cannot be rolled back as it is a DDL operation and not a DML operation like DELETE.
• B is incorrect because TRUNCATE TABLE does not drop any triggers; they remain in place.
• E is incorrect as TRUNCATE TABLE may or may not release the space depending on whether the REUSE STORAGE clause is used.
• F is incorrect because FLASHBACK TABLE cannot be used to retrieve data after a TRUNCATE TABLE operation since it does not generate redo logs that FLASHBACK relies upon.

Given the statements, the failure to execute would be due to improper SQL syntax or logical structuring of the JOIN clause:

• A. SELECT * FROM employees e JOIN department d WHERE e.department_id=d.department_id AND d.department_id=90: This statement will fail because it incorrectly uses the JOIN syntax without an ON clause, which is necessary to specify the condition on which the tables are joined. This statement mistakenly places the join condition in the WHERE clause without using ON.

Correct options (executes successfully):

• B: Correctly formulated JOIN with ON and an additional condition in the WHERE clause.
• C: Incorporates the filtering directly in the ON clause, which is a valid method to restrict the rows returned by the JOIN based on conditions related to both tables.
• D: Although it appears awkward due to the order of conditions in the ON clause, it is syntactically correct.

These answers reflect typical use and constraints in SQL queries and are aligned with Oracle Database 12c standards for SQL syntax and operations.

In Oracle SQL, aggregation functions such as AVG and MAX cannot be nested directly inside each other and must be used in conjunction with GROUP BY on the column(s) that are not included in the aggregate function. Also, the HAVING clause filters groups after aggregation is applied.

A. This query will not execute successfully because it improperly nests MAX inside AVG. Oracle SQL does not allow this type of nested aggregation without a subquery.

B. This query will not execute successfully for the same reason as A, it improperly nests MAX inside AVG.

C. Similar to A and B, this query improperly nests SUM inside MAX, which is not allowed without a subquery.

D. This query will execute successfully. It filters rows based on the HIRE_DATE using a correct date format (assuming '9' refers to '09' or '1999' due to the NLS_DATE_FORMAT being 'DD-MON-RR'), then groups the remaining rows by DEPT_ID and calculates the sum of SALARY for each department.

E. This query will not execute successfully because it improperly nests MAX inside AVG without a subquery, and it incorrectly attempts to GROUP BY SALARY, which is already being aggregated.

References:

• Oracle Database SQL Language Reference, 12c Release 1 (12.1): "Aggregate Functions"
• Oracle Database SQL Language Reference, 12c Release 1 (12.1): "GROUP BY Clause"
• Oracle Database SQL Language Reference, 12c Release 1 (12.1): "HAVING Clause"