Working with Data. L1 Introduction to Database & SQL

Size: px

Start display at page:

Download "Working with Data. L1 Introduction to Database & SQL"

Solomon Webster
6 years ago
Views:

1 Working with Data L1 Introduction to Database & SQL Agenda Admin stuff Structure & Schedule of Module Assessment What tools and software is available? 1

2 Why? What is Data? Is Data Important? But is it really? Why is it important for you? 2

3 Why? What is a Database? Are Databases Important? Are they really? What is Data Mining It is the non-trivial extraction of previously unknown and potentially useful information from data Fayyad 3

4 Who has used a database today? What data are they recording? What data is stored in these databases 7 What do we need to do Data Mining? Where do we get it/data from? What are the challenges? 4

5 But!!! Data Mining: On What Kinds Of Data? Relational database Data warehouse Transactional database Advanced database and information repository Object-relational database Spatial and temporal data Time-series data Stream data Multimedia database Text databases & WWW 5

6 The KDD Process The KDD Process with a Data Warehouse Knowledge Data Mining Evaluation & Presentation Databases Data Warehouse Cleaning & Integration Selection & Transformation 6

7 CRISP-DM When do we use a Database? 7

8 8

http://www.forbes.com/sites/gilpress/2016/03/23/data-preparation-most-time-consuming-least-enjoyable-data-science-task-surveysays/#63fab32c7f75 What is a Database?

9 What is a Database? Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization. Shared collection can be used simultaneously by many departments and users. Logically related - comprises the important objects and the relationships between these objects. Description of the data the system catalog (meta-data) provides description of data to enable data independence 18 9

10 Schema on Write vs Schema on Read 19 Why model data? You need to know and understand your data Within the context of your business 10

11 11

12 Components of a DMBS

conceptual schema without having to change the external schemas Physical Schema Physical data

13 Database Basics Core Features These are the basic reasons you pay license fees for commercial Databases External View Conceptual Schema External View Logical data independence change the conceptual schema without having to change the external schemas Physical Schema Physical data independence change the internal/physical schema without having to change the conceptual schema 13

com/oralytics SQL Language DDL Data Definition Language

14 What is common between all Databases The one language to rule all your data SQL Language DDL Data Definition Language CREATE ALTER DML Data Manipulation Language SELECT INSERT UPDATE DELETE MERGE - UPSERT 14

15 DDL Data Definition Language create table STUDENT ( student_number VARCHAR2(20) PRIMARY KEY, first_name VARCHAR2(20), surname VARCHAR2(20), dob DATE, prog_code VARCHAR2(6)); DDL Data Definition Language alter table STUDENT add _address varchar2(50); alter table STUDENT add county varchar2(20); 15

16 DML - Data Manipulation Language select * from student; select * from where student_number = 'D '; select count(*) from student; select county, count(*) from students group by county; DML - Data Manipulation Language insert into STUDENT (student_number, first_name, surname, dob, prog_code) values ('D ', 'Brendan', 'Tierney', to_date('19/01/1995', 'DD/MM/YYYY'), 'DT228B'); insert into student as select a, b, c, d, e from some_other_able; 16

17 DML - Data Manipulation Language -- updates all records update STUDENT set prog_code = 'DT228A ; -- updates the records that match the where condition update STUDENT set prog_code = 'DT228A where student_number = 'D '; DML - Data Manipulation Language -- delete all the records delete from student; -- delete one (or more) matching record delete from STUDENT where student_number = 'D '; -- delete using wildcard. Deletes all matching records delete from STUDENT where first_name like 'D%'; 17

18 ER Diagram X ER Diagram in Oracle Data Modeller 18

19 Exercise For each of the following descriptions, give an appropriate ER diagram 1. Each company operates four departments and each department belongs to one company 2. Each department may or may not employ one or more employees, and each employee is employed by one department 3. Each employee may or may not have one or more dependents and each dependent belongs to one employee 4. Each employee may or may not have an employment history 19

Chapter 1 Database System Concepts and Architecture. Nguyen Thi Ai Thao

Chapter 1 Database System Concepts and Architecture Nguyen Thi Ai Thao thaonguyen@cse.hcmut.edu.vn Spring - 2016 Contents 1 -based Approach and Database Approach 2 Three-Schema Architecture and Data Independence