CS2008/CS5035 Exam Preparation

Dept. of Computing Science, University of Aberdeen2 Organization of Lecture Notes Group 1 - SQL –L1 – Introduction –L2 – Relational Model –L3 – SQL –I - SQL Introduction –L4 – SQL –II – Aggregate Functions, Sub-queries –L5 – SQL – III - Joins –L6 - SQL – IV - Data Definition & Integrity Constraints – Create Table etc –L7 – SQL –V - Access Control & Views –Additional lecture notes on writing SQL select queries Group 2 – Database Design –L8 – Database Design: ER Modelling –L9 – Database Design: ER Modelling (Continued) –L10 – Logical Design –L11 – Normalization Group 3 – Database Connectivity –L12 – Database Programming – JDBC –L13 – Introduction to Web-based DBMS Technology –L14 – Web-based Database Programming with PHP Group 4 – Database Internals –L15 – Database Security –L16 – Transaction Management –L18 – Query Processing –L19 – File Organization & Indexing –L20 – B+-Trees Group 5 – Systems/Applications –L21 – MySQL –L22 – Spatial Databases

Dept. of Computing Science, University of Aberdeen3 Exam Structure Exam Paper: Answer 2 out of 3 questions in 2 hours –Q1: Database Design –Q2: SQL + Other –Q3: Other ‘Other’ could mean anything else in the course !! –DBMS internals, Database connectivity (JDBC, PHP) and Spatial databases Your strategy should be to –Take 5-10 minutes to look over the whole paper first –Then, aim for about 55 minutes per question

Dept. of Computing Science, University of Aberdeen4 Question Structure The questions aim to test your knowledge and understanding Each question (25 marks) will be divided approximately into 3 levels: –Bookwork: (<6) – “knowledge” - what all of you should know! –Seen: (10) – “understanding” - can you solve a problem you've seen ? –Unseen: (9) – “knowledge & understanding” – solving an unseen problem For a “pass”, you'll need to get about 12/25... For a “first”, you'll need to get about 20/25 or more.

Dept. of Computing Science, University of Aberdeen5 Marking Strategy You can exploit the way examiners mark papers... Most examiners, including me, “work towards the middle”: –We try to give marks for poor answers –We try to take away marks from good answers –Intermediate answers are hardest to mark! Your strategy should be to make the examiners work as hard as possible: –Always attempt every part of your chosen 2 questions!! Record all the known facts and try to derive any new facts – required solution could be among the derived facts –If you have time at the end, go back and check your answers!!

Dept. of Computing Science, University of Aberdeen6 Common Questions Will there be any essay-type questions ? –No - but some answers may need a short paragraph Will there be a question on topic X ? –Maybe Will there be any PHP/Java/JDBC programming questions ? –No, but you should be prepared to answer general questions on any of these areas Do I need to memorise all those SQL statements ? –You should know how to use common DML/DDL/DCL statements, especially SELECT, and be able to say what most other statements do... For a “pass” you just need to learn SELECT statements in all its forms For a “first” you should learn all the SQL statements

Dept. of Computing Science, University of Aberdeen7 More Questions Will we have to draw any diagrams ? –Probably - you will not be required to draw complex figures, but you might be asked for a sketch to illustrate your answer... Do we need to read more about Spatial Databases ? –No - The lecture notes should be enough. –Same for MySQL and B+Trees Can we get solutions for past papers ? –No - we never give out exam paper solutions: the main reason is we sometimes want to re-use questions!!

Dept. of Computing Science, University of Aberdeen8 Example “Bookwork” Questions Describe the difference between file-based and database systems (3). Describe the three major abstractions in EER modelling (3). The various language statements in SQL are often classified as DDL (Data Definition Language), DML (Data Manipulation Language), and DCL (Data Control Language) statements. Give one simple example of each type of statement (3). In SQL, explain the difference between: DELETE FROM Staff; and DROP TABLE Staff; (2).

Dept. of Computing Science, University of Aberdeen9 Example “Seen” Questions Transform the EER fragment shown below into a set of relations and show the primary and foreign keys of each resulting table (6). Briefly explain how relational database query engines use relational algebra to find efficient strategies to execute SQL queries (5). The tables below describe the nuts and bolts stocked by a small hardware shop. (i) Write an SQL query to show the different types of nut stocked (3). (ii) Write an SQL query to select all the types of nut which will fit a 6mm-thread brass bolt. (5) In spatial databases, explain with the aid of a sketch how a bounding box index can help accelerate the search for objects within a given query window (5).

Dept. of Computing Science, University of Aberdeen10 Example “Unseen” Questions Given the set of related entities with attributes specified in Figure X, create a hierarchy with them. Discuss why some entities do not fit into your hierarchy (6). With reference to the hardware shop tables, the following query selects the suppliers of brass bolts costing less than 5p each: SELECT S.Name FROM Supplier S, Bolt B WHERE S.Id = B.SupplierNo AND B.Price < 0.05; Using the usual relational algebra notation, write this query in relational algebra in three different but equivalent ways. You may use the given table aliases in your answer (6).