Changed 1z0-071 Exam Questions

Oracle's interval data types store a period of time. When you want to format an interval as a string, you can use the TO_CHAR function.

A. This statement will not execute successfully because TO_DATE expects a string representing a date, not a number derived from an interval.

B. This statement will not execute successfully because TO_NUMBER does not support interval data types as an input.

C. This statement will not execute successfully because TO_DATE does not support interval data types as an input.

D. This statement will not execute successfully because TO_NUMBER expects a number or a string representing a number as an argument, not a date.

E. This statement will execute successfully. TO_CHAR function can be used to convert interval values to a formatted string, such as 'HH24:MM'.

D. True. The NVL function can replace a NULL value with a specified value, and it does not require the data types to match exactly, allowing implicit conversion where possible. Here, 'DATE' is a string literal, and 200 is a number, and since the selected column is NULL, NVL will return 200.

The other options are incorrect because the COALESCE function requires all arguments to be of the same data type or at least compatible types that Oracle can implicitly convert. In A and E, the use of COALESCE with a string literal 'DATE' and SYSDATE (which is a date type) is not compatible without explicit conversion. Option C has a typo (TRCH instead of FROM) and is mixing data types incorrectly.

Unused columns are a feature in Oracle that allows a column to be marked as unused without immediately dropping it from the table structure. The key points for each option are:

A. The DESCRIBE command does not display unused columns. These columns are also not visible in user_tab_cols but are visible in user_unused_col_tabs.

B. Primary key columns can be set to unused, but you must drop the primary key constraint before doing so.

C. Once a column is marked as unused, it is not possible to query it, and Oracle will not allow DML operations on that column.

D. This is true. Once a column is set to unused, you can add a new column with the same name because Oracle essentially considers the unused column as removed from the table.

E. Just like primary key columns, a foreign key column can be marked as unused, but you must drop the foreign key constraint first.

F. This is true. Unused columns retain their data until the column is dropped using the DROP UNUSED COLUMNS command.

References:

Oracle Database SQL Language Reference, 12c Release 1 (12.1): "ALTER TABLE"

Oracle Database Administrator’s Guide, 12c Release 1 (12.1)