Databases and PHP. Storing and Retrieving information

Transcription

1 Databases and PHP Storing and Retrieving information

2 A database is just information or data stored in a structured manner Database goa: To organize some data in a manner that makes it easy to reate, store, and retrieve the data

3 Many different companies make databases toos that aow you to create, modify, and destroy databases: Orace (eading database) MS SQL Server MySQL (open source) IBM DB2 MS Access FieMaker Pro (cross patform)

4 What do we need to know about databases? How to create a database How to use and update a database

5 Basic Database structure: A database is a coection of tabes A tabe contains a set of records A records have the same number of fieds Each fied contains a particuar piece of data

6 Exampe: consider some random data that you want to store Names (ike Joe Smith) Birth date (such as 18 Aug 1970) Favorite coor (eg, bue) Put our data in categories: Name Birth_Date Fave_Coor

7 Now organize our data in tabes. Each row wi represent one person. Caed a record. Each coumn wi represent one type of data. Caed a fied.

8 Our exampe: A fied Name Birth_Date Fave_Coor A record Joe Smith 18 Aug 1970 bue

9 Adding more records: A fied Name Birth_Date Fave_Coor A record Joe Smith 18 Aug 1970 bue Mary Smith 23 Jan 1973 Red Jane Smith 35 Apri 1985 Green

10 Need to be abe to uniquey identify records. Name fied won t work; two peope may have the same name. May have to add a unique fied, ike ID: ID Name Birth_Date Fave_Coor 1 Joe Smith 18 Aug 1970 Bue 2 Mary Smith 23 Jan 1973 Red 3 Jane Smith 35 Apri 1985 Green 4 Joe Smith 9 Feb 1987 Purpe The unique fied is caed a key fied.

11 A database may have many tabes A reationa database aows reationships to exist between tabes Reationships occur because the tabes have fieds in common (the keys). It is more efficient to create mutipe tabes and have reationships than it is to create one arge tabe or to repeat data in tabes

12 Exampe: a product database. Cust_ID Name Add 125 Mike 1212 Main St. 268 Jim 458 Bee Ave. 381 Nancy st St. Prod_id Tite Descript price Hat Warm Jacket Waterpro of Shirt Coorfu Pants Peated Socks Woo Order_ID Customer Prod_ordered Quantity Red indicates a key fied

13 Exampe: a product database. Cust_ID Name Add 125 Mike 1212 Main St. 268 Jim 458 Bee Ave. 381 Nancy st St. Prod_id Tite Descript price Hat Warm Jacket Waterpro of Shirt Coorfu Pants Peated Socks Woo Order_ID Customer Prod_ordered Quantity Red indicates a key fied

14 Database Normaization Database normaization is a set of rues These rues make you organize your DB such that tabes are a reated and fexibe Set of rues are caed norma forms If the first three sets of rues or normaization are foowed, the database is said to be in third norma form

15 Database Normaization Fat tabe No organization of data No mutipe tabes A data in one giant tabe Like a spreadsheet with many coumns for data

16 Database Normaization Fat tabe exampe: data repeated, no reationships Student Name CourseID1 Course Description1 Course Instructor1 CourseID2 Course Description 2 Course Instructor2 Etc. George Stuff Abert Junk Susan Juie Junk Susan Stars Abert Sam Stuff Abert Junk Susan Jessica Stars Abert Stuff Abert Note a the dupication!

17 Database Normaization First Norma Form Eiminate repeating information Create separate tabes for reated data Exampe tabe has two main topics: Students Courses First norma form exampe woud create two tabes Students (students) Students + courses (students_courses)

18 Database Normaization 1-to-many reationship: one student to many courses Number of courses a student may take is now not imited to the number of coumns in the tabe. students tabe StudentID StudentName George Juie StudentID CourseID Course Description Course Instructor Stuff Abert Junk Susan Junk Susan students_courses tabe Stars Abert

19 Database Normaization Second Norma Form No non-key attributes depend on a portion of the primary key. ie, if fieds in your tabe are not entirey reated to a primary key, they must go. In our exampe: students shoud not be in the courses tabe. Now have three tabes: Students tabe (as before) Courses tabe (course ID, description, instructor) Student_Courses tabe (student id, course id)

20 Database Normaization 1-to-many reationship: one student to many courses students tabe StudentID StudentName George Juie CourseID Course Description Course Instructor StudentID CourseID Stuff Abert Junk Susan Junk Susan Stars Abert courses tabe students_courses tabe

21 Database Normaization Third Norma Form No attributes depend on other non-key attributes. Ie, see if more fieds exist that can be broken down further and that aren t dependent on a key. Think about removing data In our exampe: instructors Instructors can teach more than one cass However, the courseinstructor fied in the courses tabe is not a key of any sort. So can break this fied out into its own tabe In reaity, woud have more info about instructors (instructorid, etc.) that woud go into this new tabe.

22 Database Normaization Third Norma Form No attributes depend on other non-key attributes. 1-to-many reationship: one student to many courses 1-to-many reationship: one instructor to many courses. Now have 4 tabes: Students tabe (as before) Courses tabe (course ID, description, instructor) Student_Courses tabe (student id, course id) Instructors tabe (instructor ID, name)

23 Database Normaization instructors tabe InstructorID InstructorName Abert Susan students tabe StudentID StudentName George Juie CourseID Course Description Instructor ID Stuff Junk Stars courses tabe StudentID CourseID students_courses tabe