To answer this question, you need to understand the concept of the CURSOR FOR loop in programming.

The correct answer is D) None.

In Oracle PL/SQL, the command used to open a CURSOR FOR loop is not explicitly mentioned. The CURSOR FOR loop implicitly opens the cursor and fetches the rows from the cursor one by one until there are no more rows to fetch. The syntax for the CURSOR FOR loop is as follows:

FOR  IN 
LOOP
    -- Statements to process each fetched row
END LOOP;

So, there is no specific command used to open the CURSOR FOR loop in Oracle PL/SQL. The loop itself takes care of opening and fetching the rows from the cursor.

Therefore, the correct answer is D) None.

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• Wrong explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) A function must return a value - This option is correct. A function is a subprogram that performs a specific task and returns a value. When a function is executed, it calculates a value and returns it to the calling program.

Option B) A procedure must return a value - This option is incorrect. Unlike a function, a procedure does not have to return a value. A procedure is a subprogram that performs a specific task, but it does not return a value.

Option C) A function executes a PL/SQL statement - This option is incorrect. A function can execute multiple PL/SQL statements, but it is not limited to executing only PL/SQL statements. A function can also perform calculations, access database tables, and perform other operations.

Option D) A function is invoked as part of an expression - This option is correct. A function can be called within an expression to perform a specific calculation or operation. The result of the function call is then used as part of the overall expression.

Option E) A procedure must have a return data type specified in its declaration - This option is incorrect. As mentioned earlier, a procedure does not have to return a value. Therefore, it does not require a return data type to be specified in its declaration.

The two statements that are true are Option A) A function must return a value, and Option D) A function is invoked as part of an expression.

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• Wrong explanation

To answer this question, you need to understand the concept of trigger timing in database systems.

In Oracle, trigger timing refers to when a trigger is fired during the execution of a SQL statement. There are two types of trigger timing: statement-level and row-level.

Statement-level triggers are fired once for each triggering statement, regardless of the number of rows affected by the statement. These triggers do not have access to the individual rows that were affected by the statement. Therefore, you cannot reference the NEW and OLD qualifiers in statement-level triggers.

On the other hand, row-level triggers are fired once for each affected row within the triggering statement. These triggers have access to the individual rows that were affected by the statement. In row-level triggers, you can reference the NEW and OLD qualifiers to access the new and old values of the affected rows.

Based on this information, the correct answer is:

C. Row only - This option is correct because you can reference the NEW and OLD qualifiers in row-level triggers, but not in statement-level triggers.

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• Wrong explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) The COMMIT and ROLLBACK commands are allowed in the packaged function. - This option is incorrect. In a packaged function used in a query, you cannot use the COMMIT and ROLLBACK commands because they are transaction control commands and are not allowed in a query context.

Option B) You cannot use packaged functions in a query statement. - This option is incorrect. Packaged functions can be used in a query statement.

Option C) The packaged function cannot execute an INSERT, UPDATE, or DELETE statement against the table that is being queried. - This option is correct. Packaged functions used in a query cannot execute any DML (Data Manipulation Language) statements like INSERT, UPDATE, or DELETE against the table that is being queried. They are only allowed to perform read operations.

Option D) The packaged function can execute an INSERT, UPDATE, or DELETE statement against the table that is being queried if it is used in a subquery. - This option is incorrect. Packaged functions used in a query cannot execute any DML statements, even if they are used in a subquery.

Option E) The packaged function can execute an INSERT, UPDATE, or DELETE statement against the table that is being queried if the pragma RESTRICT REFERENCE is used. - This option is incorrect. The pragma RESTRICT REFERENCE is used to restrict the ability of a packaged function to modify data. However, even with this pragma, a packaged function used in a query cannot execute any DML statements against the table being queried.

The correct answer is C) The packaged function cannot execute an INSERT, UPDATE, or DELETE statement against the table that is being queried. This option is correct because packaged functions used in a query are restricted to read operations only.

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• Wrong explanation