KC7013: Database Modelling - Computer Science Assignment Help

Assignment Task:

Assignment Questions

Part 1: Implementing the object-relational database for AiS 

This part is based on the ‘AiS’ scenario as described in Appendix 1.

(A) Using object-oriented/extended entity-relationship modelling, produce a conceptual and logical database model for AiS. 

You have the option to produce a fresh conceptual and logical database model using object-oriented or extended entity-relationship modelling or incorporate advanced entity modelling concepts (e.g., aggregation & composition, inheritance or generalisation/specialisation/, etc) into your entity-relationship model for AiS from your assignment 1.

(B) Create an object-based database for AiS using object-relational (O-R) features of Oracle 10g//11g/12c based on the conceptual and logical database model from (A) above.

Note that all relationships (e.g., one-to-one, one-to-many, many-to-many) must be bi-directional. Moreover, each to-many side of a relationship (e.g., in case of many-to-one and many-to-many) should be implemented using nested tables. In addition, your implementation should allow all objects to be shareable (i.e. all relationships should be REF based). Oracle (2005a) provides more detailed documentation on Oracle object-relational features. 

(C) Populate the O-R version of your database using data from the relational version of the AiS database you developed in Assignment 1.

Using PL/SQL and/or SQL, populate your O-R database by querying the relational tables you implemented earlier during your Assignment 1 solution. This task can be seen to contain the following sub-tasks:

(i) Creating/inserting objects in your object tables.

(ii) Populating one-to-many, many-to-one, and many-to-many relationships among the objects created in sub-task (i)

(D) Query the O-R version of your AiS database

For this part, you must use PL/SQL procedures (2 procedures, each worth 4 marks). Answer the following questions after populating the object-relational database:

1. Display names of students, details of the course they study, details of the module they have studied and their marks for all postgraduate students.

2. Display details of all people of ‘AiS’ (students and academic staff), e.g., their names, their home addresses and name of the department where they work or study.

NOTE the following important points for Part 1 (A to D):

• You must submit all the SQL and PL/SQL code used for creating, populating and querying the O-R database.

• You must submit the output of running your code (e.g., SPOOL files).

(E) Compare and contrast your relational and object-relational versions of the AiS database. You should highlight the advantages and disadvantages of both versions. Comment on which version will best suit the AiS database.

Part 2:  Data Warehousing Tasks 

This part is based on the Sales History scenario as described in Appendix 2.

You must submit all the SQL queries and any other code that you wrote in answering any of the tasks/questions (e.g., the use of Explain Plan statements for the queries and their SPOOL outputs).

1. Study the index definitions in sh_idx.sql. Discuss in detail (using cost-based analysis) why these indexes (at least two of them) are useful for answering queries over the SH2 and DWn versions of the database. You should not run the sh_idx.sql script at all under any circumstances as it will interfere with your cost-based analysis of query performance in Part 2 of this assignment.                                                              

2. Identify two new indexes and justify why they could be useful. Write the SQL code for creating these indexes under your DWn user. Give example queries with cost-based analysis for both DWn (which will have the new indexes) and SH2 users (which will not have any of your new indexes).

3. Given the materialized views (MVs) defined in sh_cremv.sql, discuss in detail why these MVs are useful for users of the SH database. You should provide detailed examples (cost-based analysis, e.g., using Explain Plan for running sample queries on both SH2 and DWn) to illustrate your answer. You should not run the sh_cremv.sql script at all under any circumstances as it will interfere with your cost-based analysis of query performance in Part 2 of this assignment.                                                               

4. Identify two other MVs based on the base tables in the SH schema under your DWn user and justify why they would be useful. Write the SQL code for creating these MVs.

5. Prior to the introduction of the aggregation function ROLLUP, there was no possibility to express an aggregation over different levels within one SQL statement without using the set operation UNION ALL. Every different aggregation level needed its own SQL aggregation expression, operating on the exact same data set n times, once for each of the n different aggregation levels. With the introduction of ROLLUP in the recent editions, Oracle provided a single SQL command for handling the aggregation over different levels within one single SQL statement, not only improving the runtime of this operation but also reducing the number of internal operations necessary and reducing the workload on the system.

6. Using ROLLUP, write an SQL query over the SH schema under your DWn user involving one fact table (SALES or COSTS) and at least two dimension tables. Provide reasons why your query may be useful for users of the SH data warehouse.

7. Using set operation UNION ALL (and not ROLLUP), write an SQL query that produces the same result as the query in (a) above. 

8. Using EXPLAIN PLAN, provide a detailed discussion analysing costs of evaluating the above queries (i.e. with and without ROLLUP).

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