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Introduction

Introduction. Storage Temporary and Permanent Unstructured and Structured Ways to structure information Simple databases Relationships, example relationship Some Database Terminology SQL – Structured Query Language. Storage – Temporary and Permanent.

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Introduction

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  1. Introduction • Storage • Temporary and Permanent • Unstructured and Structured • Ways to structure information • Simple databases • Relationships, example relationship • Some Database Terminology • SQL – Structured Query Language

  2. Storage – Temporary and Permanent • Many applications store information for later use • Storage may be temporary or permanent • Permanent storage is usually in the form of a file (e.g. a plain text file) stored on a physical disc drive • Many applications add, modify and retrieve information from structured data stores, often called databases

  3. Storage – Unstructured and Structured • Unstructured information (e.g. the stream of words in a speech) is easy to store in a plain text file • Structured information (name, occupation, date of birth, eye colour – for a set of people) is easy to store in a database • What is the advantage of using a database? (The personal information could be stored in a text file, after all.)

  4. Ways to structure information • A lot of collected data is repetitive in form • Data may be repetitive in content, too • For example, if we have the following information for 15 people; [Age in years], [Name], [Height in metres] then we have 15 records of 3 fields, in this format; [whole number], [text], [fractional number]

  5. More example information • Here is some simple information: Danny DeVito(USA), Hugh Jackman (Australia), Halle Berry(USA), Patrick Stewart (UK), … • This kind of information has a simple structure or format • We can put the information into a table

  6. Table (with repeated information)

  7. Table (no repeated information) This is an example of a simple one-to-many relationship.

  8. Table (with repeated information)

  9. Tables (repeated information) This is an example of several linked tables

  10. Repeated Information • The previous example does not solve the problem • What about the other actors/actresses in the films? • Databases can soon get complicated • Need to think carefully about structure before you start – may be difficult later on • DSA will only need simple structures in DB

  11. Some Database Terminology • Rows and Columns • Broad view of the table – each row is a record, each column is a set of fields • This is analogous to a spreadsheet view • Records and Fields • Detailed view of the information • Each record (entry) in the database is made up of fields, possibly with some fields from joined tables

  12. Relationships and Joins • Tables may be joined together – this is very powerful but can get complex • Database systems which allow join relationships are known as Relational Databases (see RDSD) • To build, use and maintain joins between tables, it is often easiest to use tools built into database programs (e.g. MS Access, SQLyog)

  13. SQL – Structured Query Language • Structured Query Language is the language of databases • It is very widely used in industry – look for mySQL, PL/SQL, SQLplus, Oracle SQL and so on • We can use little chunks of SQL in our applications to ask a database for information (i.e query the database)

  14. Structured Query Language • Structured Query Language (SQL), is a set of commands that all programs and users may use to access data within databases • Application programs and tools often allow users to access SQL databases without directly using SQL, but these applications in turn must use SQL when executing the user’s request

  15. History of SQL • In June 1970 in the Association of Computer Machinery (ACM) journal, Communications of the ACM published the paper, “A Relational Model of Data for large Shared Data Banks,” by Dr. E. F. Codd • Codd’s model is the definitive model for relational database management systems (RDBMS) • IBM Corporation, Inc. developed Structured English Query Language(SEQUEL) using Codd’s model • SEQUEL later became SQL, the standard RDBMS language

  16. What can it do? • SQL provides commands for a variety of tasks including: • querying data, • inserting, updating, and deleting rows in a table, • creating, replacing, altering, and dropping objects, • controlling access to the database and its objects, • guaranteeing database consistency and integrity.

  17. Conclusion • We need to store some information in a structured way • Simple tables are conceptually simple • Relational databases provide a powerful and convenient way to store data • Structured Query Language provides us with a way to interact with databases

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