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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.
Parameter and Keyword Description: type_name: This identifies a user-defined type specifier that is used in the subsequent declarations of the objects. AUTHID Clause:
WHEN or THEN Key Constraints Suppose a table has two columns representing a period of time throughout which the information conveyed by the other columns is recorded as having
Table Comparison - SQL The following definitions for relation comparisons: Let r1 and r2 be relations having the same heading. Then: r1 ⊆ r2 is true if every tuple of r1
set serveroutput on declare a number(5); b number(5); c number(5); begin a:=&a; b:=&b; c:=a/b; dbms_output.put_line(c); exception when zero_divide then d
Logical Operators The logical operators AND, NOT, and OR follow the tri-state logic shown in table below. The AND and OR are binary operators; NOT is a unary operator.
Introduction Oracle 9i - it was made public in the year 2001 with over 400 features, and graphics, it has merged the traditional business with modern internet application
Database Values You can use the SELECT statement to have the Oracle assign values to a variable. For Each and every item in the select list, there must be a matching, type-compa
DELETE Statement The DELETE statement eliminates whole rows of data from the specified table or view. Syntax:
Cursor Variables Similar to a cursor, cursor variable points to the current row in the result set of a multi-row query. But, dissimilar a cursor, a cursor variable can be opene
Example of ADD CONSTRAINT in SQL Example: Alternative formulation for MAX_ENROLMENTS ALTER TABLE IS_ENROLLED_ON ADD CONSTRAINT MAX_ENROLMENTS CHECK ((SELECT COUNT (*)
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