1z0-071 Exam Dumps - Oracle Database 12c SQL

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.

A self-join is used to join a table to itself, and here's why the selected answers are correct:

Option B: It can be an outer join.A self-join can indeed be either an inner or an outer join, allowing for more flexibility in how records are matched and returned, especially useful in hierarchical or sequential data scenarios.

Option E: The query must use two different aliases for the table.When performing a self-join, aliases are necessary to distinguish between the different instances of the same table in the query.

Option F: The ON clause can be used.In SQL, the ON clause specifies the conditions that match rows in a self-join, offering a clear and structured way to define how the join works.

Other options are not universally true:

Option A: It must be an inner join. Incorrect because, as explained, outer joins are also possible.

Option C: The ON clause must be used. Incorrect because the WHERE clause might also be used to specify the join condition.

Option D: It must be an equijoin. Incorrect because non-equijoins (like non-equality comparisons) can also be used in self-joins.

When creating an external table, which allows you to access data in a flat file as though it is a table inside the database, certain clauses are required:

A. the ACCESS PARAMETERS clause: This clause specifies the parameters required by the access driver to read the data files.

D. the LOCATION clause: This clause specifies the location of the data files that make up the external table.

References:

Oracle Database SQL Language Reference 12c, particularly the sections detailing the creation and management of external tables.

C: True. A SQL statement may include multiple single row subqueries in different parts of the statement, such as in the SELECT list, WHERE clause, or HAVING clause. Each subquery must independently satisfy the requirement of returning a single row to avoid runtime errors.

D: True. Single row subqueries can be used in the HAVING clause. This allows for filtering groups based on conditions evaluated against individual or aggregated values returned by the subquery. The subquery must return a single value to be valid in this context.

E: True. Single row subqueries are often placed on the right side of the comparison operator in a SQL condition. This positioning is typical because the left side often references a column or an expression related to the main query, while the subquery on the right side dynamically provides a value for comparison.

To calculate the date from a given base date with intervals, Oracle allows you to add or subtract intervals from dates. Since the NLS_DATE_FORMAT is set to DD-MM-YYYY, the output is expected to be in that format.

Option B seems to calculate a date that is 3 months and 7 days ahead of October 29, 2019, and then subtracts 360 seconds (which is 6 minutes), resulting in a time that is still within the same day.

Here's how the calculation in option B would work out:

Start date: 29-10-2019

Add 3 months: 29-01-2020

Add 7 days: 05-02-2020

Subtract 360 seconds: Since it's only a few minutes, the date remains 05-02-2020.

However, this does not match the provided result of 02-JAN-2020. We would need to consider the exact amount of time being subtracted or added to find the correct answer.

But upon reviewing the options, they all have various syntax errors such as a missing TO_CHAR function, incorrect quotes, and date formats not matching the session's NLS_DATE_FORMAT. Therefore, we would need to correct these issues to find the right answer.

Single-row functions in SQL operate on each row independently and can modify the returned value:

Option A: Incorrect. Single row functions can be used in multiple parts of a SELECT statement, including SELECT, WHERE, and ORDER BY clauses.

Option B: Incorrect. Single row functions can accept more than one argument, such as the CONCAT function, which can accept multiple string arguments.

Option C: Incorrect. They return one result for each row processed, not per table.

Option D: Correct. Single row functions can take various types of arguments including column names, literals, variables, and other expressions.

Option E: Correct. Functions can be nested within other functions, allowing complex expressions and calculations.

Option F: Correct. The data type of the result can differ from the arguments’ data types, such as the SUBSTR function returning a VARCHAR2 even when used on a number after converting it to a string.

When the NLS_DATE_FORMAT is set to DD Mon YYYY, the database expects the date string to be in the format of day, abbreviated month name, and full year.

B. The query SELECT DATE '2019-01-01' FROM DUAL; correctly returns the value 1 Jan 2019 because the ANSI date literal DATE 'YYYY-MM-DD' is independent of the NLS_DATE_FORMAT parameter.

Option A is incorrect because the TO_DATE function requires the format model to match the string literal, which it does not in this case.

Option C is incorrect because TO_CHAR is used to convert a date to a string, not a string to a date.

Option D is incorrect because without specifying that the string is a date, the result is just a string and not a date value.

Option E is incorrect because TO_DATE without a format model relies on the NLS_DATE_FORMAT to interpret the string, and YYYY-MM-DD does not match DD Mon YYYY.

A: This statement is false. A table can only have one primary key, although the primary key can consist of multiple columns (composite key).

B: This statement is true. A table can have multiple foreign keys referencing the primary keys of other tables or the same table.

C: This statement is false. A NUMBER column without data is NULL, not zero.

D: This statement is false. A column definition must specify exactly one data type.

E: This statement is true. A VARCHAR2 column without data defaults to NULL, not an empty string.