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Question:(a) The objective of query optimization is to choose the most efficient strategy for implementing a given relational query, thereby improving the system performance. One of the stages of query optimization is to convert the internal form into equivalent and more efficient canonical form, using well-defined transformation rules. Two rules of the transformation rules is given below:Rule 1 - Transform a sequence of restrictions against a given relation into a single (ANDed) restriction.Rule 2 - Transform a restriction of a projection into a projection of a restriction.(i) Explain what is meant by each of the above rules.(ii) Using the relational schema given in Appendix, provide example of each of the above rules.(b) Refer to the relational schema given in Appendix.Assuming that: The Employee relation contains 1000 records among which 300 employee are assigned to departments located in the United States.- The Department relation contains 30 records among which 20 departments are located in United States- The Location relation contains 20 records among which 5 are situated in the United States.(i) Express the following query in SQL:"find the employee Last names and the department names who are working in United States (Location.country_id = US)(ii) Choose two possible methods to evaluate the query, and use the relational algebra to formulate clearly all the steps required in the evaluation. For each method, calculate the number of tuples for all the intermediate relations (namely, size of the intermediate relations) required for each step.
Using %TYPE The %TYPE attribute gives the datatype of a variable or the database column. In the example below, the %TYPE gives the datatype of a variable: credit REAL(7,2); debi
Running the PL/SQL Wrapper To run the PL/SQL Wrapper, go through the wrap command at your operating system prompt by using the syntax as shown: wrap iname=input_file [oname=
Using a join on 3 tables, select 5 columns and 10 rows from the 3 tables without the use of a Cartesian product Query: SELECT E.LAST_NAME, E.FIRST_NAME, S.BUILDING, S.BRAN
Data Types in SQL - Character CHARACTER or, synonymously, CHAR, for character strings. When this type is to be the declared type of something (e.g., a column), the permissible
How Bulk Binds Improve Performance The assigning of values to the PL/SQL variables in SQL statements is known as binding. The binding of the whole collection at once is know
How Calls Are Resolved? The figure shows that how the PL/SQL compiler resolves the subprogram calls. When the compiler encounters the procedure or function call, it tries to di
Using Host Arrays The Client-side programs can use anonymous PL/SQL blocks to bulk-bind input and output host arrays. However, this is the well-organized way to pass the colle
Using the BULK COLLECT Clause The keywords BULK COLLECT specify the SQL engine to bulk-bind output collections before returning them to the PL/SQL engine. You can use these ke
Example of Table Literal - SQL Example: A Table Literal (correct version) VALUES ('S1', 'C1', 'Anne'), ('S1', 'C2', 'Anne'), ('S2', 'C1', 'Boris'), ('S3', 'C3'
Recursion The Recursion is a powerful method for simplify the design of the algorithms. Principally, the recursion means the self-reference. In the recursive mathematical serie
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