Online 1z0-071 Questions Video

The LOCALTIMESTAMP function in Oracle Database returns the current date and time in the session time zone. Given that the session time zone was set to -5:00 with the ALTER SESSION SET TIME_ZONE command, LOCALTIMESTAMP will return the date and time adjusted to this session time zone.

The SYSDATE function, on the other hand, returns the current date and time from the operating system of the database server, which is not affected by the session time zone setting. In the result shown, SYSDATE returns 11-JUL-2019 11:00:00, which reflects the system time zone, not the session time zone.

The time difference between the DBTIMEZONE (+00:00) and the session time zone (-5:00) is 5 hours. Since SYSDATE shows the time as 11:00:00 in the system time zone, the LOCALTIMESTAMP adjusted to the session time zone would show the time as 06:00:00.

The correct answer is A: 11-JUL-2019 6:00:00.00000000 AM – 05:00. This represents the local timestamp in the session time zone, which is 5 hours behind the DBTIMEZONE.

Please note that the exact format returned by LOCALTIMESTAMP includes the fractional seconds up to 9 decimal places, and the time zone offset is specified as part of the timestamp.

Understanding the functionality of SQL joins and their application in a relational database:

Option A: Correct. A self join is used to relate or compare rows within the same table. It typically involves using table aliases to distinguish the different instances of the table in the query.

Option B: Incorrect. An inner join relates rows between two different tables based on a common condition, not within the same table.

Option C: Incorrect. SQL allows joining of rows from any tables, whether directly related by foreign keys or not, as long as there is a logical condition that can relate their columns.

Option D: Correct. Sometimes establishing a relationship between two specific tables might require joining through one or more intermediary tables, particularly in cases involving complex relationships or normalization.

Option E: Incorrect. While joins are often used to implement relationships, not every logical relationship necessitates a join condition, especially if data from only one table is required or if multiple relations are possible but not relevant to the specific query.

Set operators allow you to combine multiple queries into a single query. The key points for each option are:

A. An expression in the first SELECT list does not need to have a column alias; however, the column alias given to an expression in the first SELECT list is used as the column name of the output.

B. This statement is true. When CHAR columns of different lengths are combined with a set operator, Oracle will pad the shorter values with spaces to match the length of the longest value. This behavior is consistent with the SQL standard and Oracle's treatment of the CHAR datatype.

C. Oracle Database performs implicit conversion between compatible data types where necessary when using set operators. For example, a NUMBER can be implicitly converted to a VARCHAR2 and vice versa if the context requires it.

D. This is true. When multiple set operators are used in a single query, the INTERSECT operator takes precedence over the UNION and UNION ALL operators. This order of operation can be overridden by using parentheses.

E. Not all set operators work with all data types. For instance, LOB and LONG RAW data types cannot be used with set operators.

References:

Oracle Database SQL Language Reference, 12c Release 1 (12.1): "Set Operators"

Oracle Database SQL Language Reference, 12c Release 1 (12.1): "Data Types"

For SQL queries involving set operations like UNION, UNION ALL, INTERSECT, and MINUS, the data types and number of columns in the SELECT statements being combined must be the same. Here is a breakdown of each query option:

Option A: This query successfully combines results from two tables using UNION ALL, which combines all rows from both SELECT statements, including duplicates. Both queries select two columns (prod_id and exp_date, with exp_date being NULL in the second query). This is valid as the number of columns and their data types match.

Option B: This query attempts to use INTERSECT, which returns only the rows common to both SELECT statements. However, the first SELECT statement chooses prod_id and prod_name, while the second only substitutes a constant value for prod_id without specifying from which table it selects prod_name. If "newproducts" (presumably a typo and should be "new_products") does not have the exact columns as "products", or if the data types do not match, it will fail.

Option C: This query uses UNION, which removes duplicates from the combined dataset. The use of SELECT * assumes that both "products" and "new_products" tables have the same columns in the same order with matching data types. This query will succeed if those conditions are met.

Option D: This query uses MINUS to subtract results of the second SELECT from the first. However, it fails because 'k' does not explicitly match a column name in "products", suggesting a potential error unless 'k' is indeed a valid column.

Option E: This query fails because the first SELECT statement fetches only one column (prod_id) while the second fetches two columns (prod_id and prod_name). UNION ALL requires the same number of columns with compatible types in all SELECT statements involved.