Full Access Oracle 1z0-071 Tutorials

To determine which queries will execute successfully, we need to consider the compatibility of the column definitions and the structure of the SELECT statements:

• Option A uses the MINUS set operator, which subtracts rows returned by the second SELECT statement from the rows returned by the first. For MINUS to work, the number and the order of columns and their data types must be the same in both queries. This query will not execute successfully because the second SELECT statement does not include all columns from the first SELECT statement, and the data types and sizes of PROD_ID do not match (CHAR(2) vs CHAR(4)).
• Option B uses the UNION ALL set operator, which appends the results of the second SELECT statement to the results of the first. Unlike UNION, UNION ALL does not eliminate duplicate rows. This query will execute successfully because UNION ALL does not require the same data types or sizes, and the result will contain all columns from the first SELECT statement filled with NULL for non-matching columns from the second SELECT statement.
• Option C uses the UNION set operator, which requires the same number of columns and compatible data types. This query will not execute successfully because PROD_NAME has different data types (CHAR(4) vs VARCHAR2(10)), and the result of a UNION must have the same number of columns with compatible data types in the two SELECT statements.
• Option D uses the UNION set operator as well, but unlike Option C, it does not require a specific data type match because both SELECT statements include all columns and UNION is used (which will automatically handle type conversion where necessary). This query will execute successfully.
• Option E uses the INTERSECT set operator, which requires the same number and order of columns and their data types to be identical or compatible. This query will not execute successfully because the data types and sizes of PROD_ID do not match (CHAR(2) vs CHAR(4)).

References:

• Oracle Documentation on Set Operators: SQL Language Reference - Set Operators
• Oracle Documentation on Data Type Precedence: SQL Language Reference - Data Type Precedence

In conclusion, only Option B and Option D will execute successfully because they adhere to the rules of the UNION ALL and UNION operators respectively, regarding column count and data type compatibility.

Data Manipulation Language (DML) operations in Oracle 12c are critical for handling data within tables. Here’s the validity of each statement based on Oracle SQL documentation:

• Option A: True. The DELETE statement can remove multiple rows from a table and supports the use of multiple conditions in the WHERE clause to specify which rows should be removed. This allows for flexibility in managing data deletion based on various criteria.
• Option B: True. The INSERT statement can explicitly insert NULL values into a column, assuming there are no constraints (like NOT NULL) preventing such entries. This is useful for representing the absence of data or when data is unknown.
• Option C: False. DML statements like INSERT INTO...SELECT...FROM do not automatically commit in Oracle. Transactions in Oracle require explicit COMMIT commands to finalize changes, unless in an autocommit mode set by a client tool or environment, which is generally not the default behavior for server-side operations.
• Option D: False. DML statements do not require a primary key to be defined on a table. While having a primary key is a best practice for identifying each row uniquely, it's not a prerequisite for performing DML operations like INSERT, UPDATE, or DELETE.
• Option E: True. The UPDATE statement can include different subqueries within the SET clause to determine the values for each column being updated. This allows for complex calculations and data retrieval to be part of an update, increasing the power and flexibility of data modification.

The UNION ALL operator in SQL is used to combine the results of two or more SELECT statements:

• Option D: It will return rows from both SELECT statements including duplicate rows.

Options A, B, and C are incorrect as they describe behaviors of other set operators:

• Option A: Describes the behavior of INTERSECT, not UNION ALL.
• Option B: Describes the behavior of UNION, not UNION ALL.
• Option C: Describes the behavior of EXCEPT or MINUS, not UNION ALL.

B: True. The Oracle Database MERGE statement can use a subquery that involves views to generate the source data for the merge operation. This allows for greater flexibility in specifying the data to be merged.

C: True. MERGE can conditionally combine rows from one or more source tables (or views, or the results of a subquery) to insert or update rows in a single target table based on whether or not a match exists.

D: True. MERGE can indeed use subqueries to produce source rows. The source data for a merge operation can be a table, view, or the result of a subquery.

The MERGE statement is a powerful SQL operation in Oracle that allows for conditional INSERT or UPDATE operations in one statement, often referred to as an "upsert" operation. It can handle complex scenarios where the decision to insert or update is based on whether the data matches between the target and source datasets.

References:Oracle SQL documentation on the MERGE statement provides information on how it can use different data sources, including subqueries and views, and perform conditional operations on the target table.