1. CSC 2720 Building Web Applications Database and SQL

2. Database and DBMS  Database – Structured collection of records or data  Database Management System (DBMS) – Specialized software for managing databases

3. Advantages of using DBMS  Efficient Data Access  Support multiple users and Data Security  Protect access to data in which only authorized users can access the data  Concurrent Access  Support mechanisms to allow multiple users to safely read/write the data. (e.g., record locking)  Transaction  Comprises of multiple indivisible operations  A transaction must succeed or fail as a complete unit; it cannot remain in an intermediate state.

4. Advantages of using DBMS  Standardized query language for defining and manipulating data  Network accessible DBMS Web App (Java Servlet) Web App (PHP) Web App (ASP.NET) Stand alone App (Java / C++ / C ) Database Management Tools SQL

5. Introduction to Relational Database  Relational Database – A type of database in which data are organized into related tables (a.k.a. relations). ItemIDNamePriceQuantity 0123456Coffee4.50100 0222222Soy Milk4.4050 0142562Tea5.0040 Row / Record Column / Field / Attribute  A table has a name.  A field has a name and a type.

6. Designing a Table – Deciding column names and types  Name  Should contain only letters, digits and underscore  Meaningful  Should not be a reserve word  Should be less than 64 characters  Should assume the name is case sensitive  Three Primary Types  Text (or Strings) – CHAR, VARCHAR, etc.  Numbers – INT, DOUBLE, DECIMAL, etc.  Dates and Times – TIME, DATE, DATETIME, etc.

7. TypeSize (bytes)Description CHAR[Length]LengthA fixed-length field from 0 to 255 characters long VARCHAR[Length]Length + 1 or 2A variable-length field from 0 to 65535 characters long TINYINT / SMALLINT / MEDIUMINT / INT / BIGINT 1 / 2 / 3 / 4 / 8 Signed integers FLOAT / DOUBLE4 / 8Single and Double precision floating point numbers DECIMAL[Length, Decimals]Length + 1 or 2A DOUBLE stored as a string, allowing for a fixed decimal point (Length: # of digits, Decimals: # of decimal places) DATE3In the format YYYY-MM-DD TIME3In the format of HH:MM:SS DATETIME8In the format of YYYY-MM-DD HH:MM:SS TIMESTAMP4In the format of YYYYMMDDHHMMSS; acceptable range ends in the year 2037 Some Common MySQL Types

8. Additional Field Properties  NOT NULL  Every field must be assigned a value or else an error will occur.  DEFAULT default_value  If a field is not assigned any value, default_value is assumed.  AUTO_INCREMENT  Use an integer that is one more than the current largest integer as the default value  UNSIGNED  A field can only hold non-negative integer.  The range of positive integers is doubled.

9. SQL query to create a "Users" table  PRIMARY KEY (user_id)  Indicates that the field user_id is to be used as the primary key to identify the records in the table CREATE TABLE users ( user_id MEDIUMINT UNSIGNED NOT NULL AUTO_INCREMENT, first_name VARCHAR(20) NOT NULL, last_name VARCHAR(40) NOT NULL, email VARCHAR(60) NOT NULL, pass CHAR(40) NOT NULL, reg_date DATETIME NOT NULL, PRIMARY KEY (user_id) )

10. Characteristics of a Table  A NULL value means no value.  When defining a table, we can set whether a field can contain a null value or not.  Keys are used to identify records in a table.  A Primary key is a field (or combination of fields) that uniquely identifies a record within a table.  A Foreign key is a field (or combination of fields) that serves as a primary key in another table. It is used to establish a relationship between a pair of tables.  Records are not ordered in a table.

11. Structured Query Language (SQL)  A language that can be used to build, modify, query, and manipulate a database  SQL supported by different DBMS may vary slightly.  With SQL, you can  Create/delete a database  Create/delete tables in a database  Retrieve data from a database  Insert new records in a database  Delete records from a database  Update records in a database

12. SQL (con't)  SQL is not case sensitive  Multiple statements are separated by semicolon  Important commands for manipulating data  SELECT - extracts data from a database table  UPDATE - updates data in a database table  DELETE - deletes data from a database table  INSERT INTO - inserts new data into a database table  Important commands for manipulating table  CREATE TABLE - creates a new database table  ALTER TABLE - alters (changes) a database table  DROP TABLE - deletes a database table  Examples: SQL Tutorial at W3Schools  http://www.w3schools.com/sql/default.asp http://www.w3schools.com/sql/default.asp