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 ' .

In the context of SQL statements using SET operations like UNION in Oracle Database 12c:

A. The data type of each column returned by the second query must be implicitly convertible to the data type of the corresponding column returned by the first query. This is correct. Oracle allows the union of columns as long as their data types are implicitly convertible, not necessarily identical.

C. The number, but not names, of columns must be identical for all SELECT statements in the query. This is correct. For a UNION operation to be valid, all SELECT statements involved must have the same number of columns, although their names and exact data types need not match.

Options B, D, and E are incorrect:

B is incorrect because exact data type matches are not required, only that they be implicitly convertible.

D is also incorrect for the same reason as B; it ' s enough that the types are compatible, not identical.

E is incorrect as the names

In SQL, when you want to count occurrences of null values using the COUNT function, you must remember that COUNT ignores null values. So, if you want to count rows with null list_price , you have to replace nulls with some value that can be counted. This is what the NVL function does. It replaces a null value with a specified value, in this case, 0.

A, C, and D options attempt to count list_price directly where it is null, but this will always result in a count of zero because COUNT does not count nulls. Option B correctly uses the NVL function to convert null list_price values to 0, which can then be counted. The WHERE list_price IS NULL clause ensures that only rows with null list_price are considered.

The SQL documentation confirms that COUNT does not include nulls in its count and NVL is used to substitute a value for nulls in an expression. So option B will give us the correct count of rows with a null list_price .

To display unique promotion costs in each promotion category, the correct queries that can be used are:

C. SELECT DISTINCT promo_category || ' has ' || promo_cost AS COSTS FROM promotions ORDER BY 1; This query concatenates the promo_category with the literal ' has ' and promo_cost , giving a unique string for each combination of promo_category and promo_cost, which is what we are interested in when we want to list unique costs per category.

D. SELECT DISTINCT promo_category, promo_cost FROM promotions ORDER BY 1; This query selects distinct combinations of promo_category and promo_cost , which is exactly what ' s required to display unique promotion costs in each category.

Options A, B, and E are incorrect:

A is incorrect because it does not use the DISTINCT keyword to ensure uniqueness.

B has incorrect syntax; the DISTINCT keyword should appear directly after SELECT and applies to all columns, not just one.

E is syntactically incorrect and would not execute because the DISTINCT keyword is not used correctly. It should not appear twice in the SELECT clause.

For creating tables and utilizing sequences in Oracle 12c SQL, certain rules apply:

Option A : This statement is valid. It creates a table with a primary key and dates, where the default value for end_date is SYSDATE. There are no constraints on sequences, and all syntax is correct.

Option B : This option is invalid because it attempts to use CURRVAL of a sequence as a default value for a primary key. CURRVAL cannot be used until the sequence ' s NEXTVAL has been called in the session.

Option C : Invalid syntax because ' start date ' is not a recognized default expression in Oracle SQL. If the intention was to use ' start_date ' as a reference, it still would not work correctly without proper syntax for conditional default values.

Option D : This syntax is invalid in Oracle SQL because the DEFAULT clause does not support relational conditions directly within the table definition.

Option E : Valid. It correctly uses NEXTVAL for a sequence in the DEFAULT clause for the primary key, ensuring that each new record has a unique primary key generated from the sequence. The start_date and end_date are assigned defaults of SYSDATE, which is syntactically correct.

The data dictionary is a read-only set of tables that provides information about the database. Certain operations that modify the database structure will cause changes to the data dictionary:

Option B : GRANT UPDATE ON scott.emp TO fin_manager;

Granting privileges on a table will change the data dictionary as it records the new privilege.

Option D : TRUNCATE TABLE emp;

Truncating a table affects the data dictionary because it removes all rows from a table and may also reset storage parameters.

Options A, C, and E do not cause changes to the data dictionary:

Option A is incorrect because the DELETE command modifies data, not the data dictionary structure.

Option C is incorrect because altering a session parameter does not change the data dictionary; it is a temporary change for the session.

Option E is incorrect because a SELECT query does not change the database, it just retrieves information.

In Oracle Database 12c, the behavior of the ORDER BY clause is guided by several rules:

Option B : An ORDER BY clause can perform a binary sort.

A binary sort is the default sorting mechanism in Oracle Database, which is based on the binary representation of the data.

Option C : An ORDER BY clause can perform a linguistic sort.

Oracle supports linguistic sorting through the use of the NLS_SORT parameter, which can be set to various linguistic and cultural norms.

Option D : By default, an ORDER BY clause sorts rows in ascending order.

If no ASC or DESC keyword is specified, Oracle will sort the results in ascending order by default.

Options A and E are incorrect:

Option A is not universally true; the position of NULL values in the sort order can be controlled by settings or specific SQL syntax ( NULLS FIRST or NULLS LAST ).

Option E is incorrect as the HAVING clause filters groups after data has been grouped by the GROUP BY clause and cannot be logically placed before ORDER BY in processing order.

A : This statement is correct. It orders the employees by salary and fetches the first 3 rows.

B : This statement has a typo with " FETCE " and " RONS " which should be " FETCH " and " ROWS " . Hence, it will not execute successfully.

C : This statement will not execute successfully due to syntactical errors and incorrect use of the ORDER BY clause.

D : This statement is correct. It uses a subquery to order employees by salary and then limits the results to the first 3 using the ROWNUM pseudo-column.

E : This statement will not execute successfully because ROWNUM is evaluated before the ORDER BY clause, so it would return the first 3 rows based on the table ' s natural order, not the lowest salaries.

The behavior of ROWNUM and the FETCH FIRST syntax are explained in the Oracle Database SQL Language Reference 12c.