Oracle 1z0-071 Exam With Confidence Using Practice Dumps

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.

In Oracle Database 12c, the operations related to dropping columns from a table include several behaviors, each specified clearly in Oracle documentation and best practices:

B. A column drop is implicitly committed: Dropping a column in Oracle using the ALTER TABLE ... DROP COLUMN command is a DDL (Data Definition Language) operation, which means it cannot be rolled back. DDL commands in Oracle are automatically and implicitly committed, meaning that once a column is dropped, the action is finalized immediately.

C. A column that is referenced by another column in any other table cannot be dropped: In Oracle, if a column is being referenced by a foreign key constraint or any dependency from another table, you cannot directly drop it until those references are removed or disabled. This ensures data integrity across related tables.

E. A primary key column cannot be dropped: The primary key constraint is critical for identifying unique rows within a table. Oracle does not allow the dropping of columns that are part of a primary key without first dropping the constraint or modifying it to exclude the column you intend to drop.

References:

Oracle Database SQL Language Reference 12c, specifically sections discussing DDL operations and constraints.

In Oracle Database 12c, the operations related to dropping columns from a table include several behaviors, each specified clearly in Oracle documentation and best practices:

B. A column drop is implicitly committed: Dropping a column in Oracle using the ALTER TABLE ... DROP COLUMN command is a DDL (Data Definition Language) operation, which means it cannot be rolled back. DDL commands in Oracle are automatically and implicitly committed, meaning that once a column is dropped, the action is finalized immediately.

C. A column that is referenced by another column in any other table cannot be dropped: In Oracle, if a column is being referenced by a foreign key constraint or any dependency from another table, you cannot directly drop it until those references are removed or disabled. This ensures data integrity across related tables.

E. A primary key column cannot be dropped: The primary key constraint is critical for identifying unique rows within a table. Oracle does not allow the dropping of columns that are part of a primary key without first dropping the constraint or modifying it to exclude the column you intend to drop.

References:

Oracle Database SQL Language Reference 12c, specifically sections discussing DDL operations and constraints.

A: 'CREATE SEQUENCE emp_seq START WITH 1 INCREMENT BY 1 NOCACHE;' is correct for ensuring unique values without gaps as much as possible by not caching sequence numbers, which might otherwise be lost in a system crash.

B: CYCLE allows the sequence to restart when its max/min value is reached, which does not help with requirement 3 (duplicates are never permitted). Therefore, B is incorrect.

C: This lacks the necessary attributes like START WITH and INCREMENT BY which are crucial to defining a sequence. Thus, statement C is incorrect.

D: 'CREATE SEQUENCE emp_seq START WITH 1 CACHE;' might introduce gaps due to the caching of sequence numbers. This statement is somewhat contrary to requirement 5.

E: 'CREATE SEQUENCE emp_seq START WITH 1 INCREMENT BY 1 CACHE;' will provide continuous unique values, but may include gaps when the cache is lost due to a restart, yet it is more efficient and still generally aligns with the requirements. Hence, statement E is considered correct.

F: This lacks detail and is too ambiguous, lacking the necessary parameters. Therefore, F is incorrect.