Oracle 1z0-071 Exam Made Easy: Step-by-Step Preparation Guide

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.

A: No implicit conversion; DATE is explicitly specified.

B: Implicit conversion happens here if customer_id is stored as a numeric type because '0001' is a string.

C: TO_DATE is explicitly used, so no implicit conversion occurs here.

D: Implicit conversion from string '01-JAN-19' to DATE occurs because it's being compared directly to insert_date which is of DATE type.

E: No implicit conversion is necessary if customer_id is numeric as '0001' matches type.

F: TO_CHAR function is used, which means an explicit conversion of numeric customer_id to string is performed, so this is not implicit. Hence, this is incorrect regarding implicit conversion.

Each answer has been verified with reference to the official Oracle Database 12c SQL documentation, ensuring accuracy and alignment with Oracle's specified functionalities.

The statements regarding data type conversions and the treatment of literals in SQL expressions involve understanding implicit and explicit data conversions in Oracle SQL.

Statement A is true as invoice_date > '01-02-2019' involves an implicit conversion of the string literal to a date type, based on the NLS_DATE_FORMAT setting, assuming the format matches.

Statement E is true because, similarly to A, invoice_date = '15-march-2019' involves an implicit conversion where the string is automatically converted to a date type according to the Oracle NLS_DATE_FORMAT or an assumed default date format.

Statements B, C, and D involve incorrect or misleading information:

B (qty_sold = '05549821') is misleading and potentially incorrect as leading zeros in a numeric context do not typically require explicit conversion but the presence of spaces might suggest a need for trimming rather than numeric conversion.

C (CONCAT(qty_sold, invoice_date)) would indeed require explicit conversion because CONCAT expects string types, and thus numerical and date values must be explicitly converted to strings before concatenation.

D (qty_sold BETWEEN '101' AND '110') uses implicit conversion where the string literals '101' and '110' are implicitly converted to numbers if qty_sold is a numeric type.

The function ADD_MONTHS(hire_date, 6) adds 6 months to the hire_date. The function NEXT_DAY(date, 'day_name') finds the date of the first specified day_name after the date given. In this case, 'MONDAY' is used to find the date of the first Monday after the hire_date plus 6 months.

Option A is correct as it accurately composes both ADD_MONTHS and NEXT_DAY functions to fulfill the requirement.

Options B, C, and D do not provide a valid use of the NEXT_DAY function, either because of incorrect syntax or incorrect logic in calculating the required date.

The Oracle Database SQL Language Reference for 12c specifies how these date functions should be used.

To calculate the total annual compensation, you need to sum the annual salary with the annual commission. The annual commission is the monthly commission percentage times the monthly salary times 12 (months). The NVL function is used to replace NULL with 0 for commission percentage when calculating the commission.

A: This statement is incorrect because it does not handle NULL values for 'monthly_commission_pct', which will result in NULL for the entire expression if 'monthly_commission_pct' is NULL.

B: This statement is syntactically incorrect because it lacks commas and proper parentheses to separate the column name 'last_ name' from the calculation.

C: This is the correct statement as it uses NVL to replace NULL with 0 and calculates the total annual compensation correctly.

D: This statement is incorrect because, like in option A, it does not handle NULL values in 'monthly_commission_pct', resulting in NULL if 'monthly_commission_pct' is NULL.

C: True. In Oracle Database 12c, character sorts are case-sensitive by default, meaning that it differentiates between uppercase and lowercase letters when sorting data. This behavior aligns with the binary collation rules typically used, unless explicitly overridden by using different collation settings.

D: True. Column aliases can indeed be used in the ORDER BY clause in Oracle SQL. This allows for more readable and maintainable code, as you can define a column alias in the SELECT list and refer to that alias in the ORDER BY clause. This usage promotes clarity, especially when dealing with complex calculations or function applications in the select list.

Single-row functions in SQL return one result per row, and the following statements are true:

A: The data type of the returned value can indeed be different from the data type of the argument provided to the function. For example, the TO_CHAR function can take a numeric input and return a character string.

B: Single-row functions can be nested within each other to any level that is supported by Oracle. This means you can have a function call as an argument to another function, and so on.

E: The argument to a single-row function can be a column name, a variable, a literal, or an expression. This flexibility allows these functions to be very powerful in SQL expressions.

The incorrect options are:

C: Single-row functions do not return a single result row per table; they return a result for each row that is processed.

D: They are not limited to accepting only one argument. Some functions, like NVL, accept multiple arguments.

F: They are not limited to use in the WHERE clause; single-row functions can be used in any part of a SQL statement, including SELECT and ORDER BY clauses.

References:

Oracle Documentation on Single-Row Functions: SQL Functions

The statement true regarding the CREATE TABLE command:

C. The NEW_SALES table would not get created because the column names in the CREATE TABLE command and the SELECT clause do not match: The SQL command tries to create a table with columns prod_id, cust_id, and order_date, but the SELECT statement specifies columns prod_id, cust_id, and time_id. The mismatch in column names and the number of columns specified will prevent the table from being created.

Incorrect options:

A: It is possible to specify a DEFAULT value in the column definition when creating a table with the CREATE TABLE AS SELECT syntax.

B: Not all NOT NULL constraints (or any other constraints, for that matter) are automatically passed to the new table unless explicitly stated in the CREATE TABLE statement.

D: FOREIGN KEY constraints are not automatically included when creating a table using the CREATE TABLE AS SELECT syntax; they would need to be added explicitly afterwards.

For the described business rule, the relationship between the students and projects entities is a many-to-many relationship, meaning that each student can be involved in multiple projects and each project can have multiple students.

Statement A is true because to implement a many-to-many relationship in a relational database, an associative (junction) table is typically used. This table will contain the primary keys from both related entities as foreign keys in the associative table, making a composite primary key consisting of STUDENT_ID and PROJECT_ID. This setup allows the database to effectively manage the relationships between students and projects.

Statement B is true as it accurately describes the solution to managing a many-to-many relationship. A direct many-to-many relationship cannot be physically implemented in a relational database. It is instead resolved into two 1-to-many relationships using an associative table as described in A. This is a fundamental relational database design principle aimed at normalizing the database and avoiding redundancy.

Statements C, D, and E are incorrect as they misrepresent the nature of the relationships and key constraints necessary for this scenario. Specifically, C and E incorrectly suggest that one entity's primary key should serve as a foreign key in another, which does not align with the many-to-many relationship requirement described. Statement D incorrectly suggests a 1-to-many relationship directly between students and projects, which does not meet the business rule requirement.