1. A Guide to SQL, Seventh Edition

2. Objectives Understand the concepts and terminology associated with relational databases Create and run SQL commands in Oracle, Microsoft Access, and MySQL Create tables using SQL A Guide to SQL, Seventh Edition

3. Objectives Identify and use data types to define columns in SQL tables Understand and use nulls Add rows to tables Describe a table’s layout using SQL A Guide to SQL, Seventh Edition

4. Introduction Databases are found at school libraries, on the Internet, and other places where you retrieve data on a computer Learn concepts and terminology associated with relational model for database management Learn how to create a database by describing and defining tables and columns A Guide to SQL, Seventh Edition

5. Introduction SQL (Structured Query Language) is a widely used language for retrieving and manipulating data SQL was developed in the mid-1970’s for IBM under the name SEQUEL Renamed SQL in 1980 Most DBMSs use a version of SQL as their data manipulation language A Guide to SQL, Seventh Edition

6. Introduction You will learn to assign data types to columns and the use of null values You will learn how to load a database by creating tables and adding data to them You will learn how to describe a table’s layout using SQL A Guide to SQL, Seventh Edition

7. Relational Databases A relational database is a collection of tables Tables are called relations This term is the basis for the name relational database A Guide to SQL, Seventh Edition

10. Entities, Attributes, and Relationships An entity is a person, place, object, event, or idea for which you want to store and process data  Premier Product’s entities are customers, orders, parts, and sales reps  Entities for a school would be students, faculty, and classes A Guide to SQL, Seventh Edition

11. Entities, Attributes, and Relationships Attribute is a character or property of an entity  Premiere Products attributes for the entity “customer” are customer name, street, city, and so on  Also called a field or column in many database systems A Guide to SQL, Seventh Edition

12. Entities, Attributes, and Relationships A relationship is the association between entities  At Premiere Products, there is a relationship between customers and sales reps  One-to-many relationship Each sales rep has many customers Each customer has only one sales rep A Guide to SQL, Seventh Edition

13. Entities, Attributes, and Relationships Premiere Products database  One table for sales reps, one for customers, and so on for each entity  Attributes become columns in each table  Relationship is represented by using common columns in two or more tables A Guide to SQL, Seventh Edition

15. Definitions A relation is a two-dimensional table in which:  Entries are single-valued  Each column has a distinct name  All values of the same attribute  Order of columns and rows is immaterial  Each row is distinct A Guide to SQL, Seventh Edition

16. Definitions A relational database is a collection of relations A row in a table is called a record or a tuple Multiple entries in one position in a table are called a repeating group A Guide to SQL, Seventh Edition

17. Shorthand Representation After the name of the table, the columns are listed within a set of parentheses  REP (Rep_Num, Last_Name, First_Name, Street, City, State, ZIP, Commission_Rate)  CUSTOMER (Customer_Num, Customer_Name, Street, City, State, ZIP, Balance, Credit_Limit, Rep_Num) A Guide to SQL, Seventh Edition

18. Shorthand Representation Not case-sensitive except when inserting character values in a table Use a period to separate the table and column name to avoid confusion The primary key uniquely identifies a row in a table Indicate primary key by underlining the column or collection of columns A Guide to SQL, Seventh Edition

19. Database Creation Describe the layout of each table in the database Use CREATE TABLE command TABLE is followed by the table name Follow this with the names and data types of the columns in the table Data types define type and size of data A Guide to SQL, Seventh Edition

20. Table and Column Name Restrictions Names cannot exceed 18 characters  In Oracle, can be up to 30 characters in length Must start with a letter Can contain letters, numbers, and underscores (_) Cannot contain spaces A Guide to SQL, Seventh Edition

21. Create Table Command A Guide to SQL, Seventh Edition

22. Create Table Command Table name is REP Contains nine columns: REP_NUM, LAST_NAME, FIRST_NAME, STREET, CITY, STATE, ZIP, COMMISSION, RATE REP_NUM is limited to two characters and is the primary key RATE column is limited to numbers, three digits with two decimal places A Guide to SQL, Seventh Edition

23. Create Table Command Commands are free-format; no rules stating specific words in specific positions Hit enter to move to the next line in a command Indicate the end of a command by typing a semicolon A Guide to SQL, Seventh Edition

24. Running SQL Commands Programs and individual preference determine method for running command Oracle 10g use SQL*Plus or SQL*Plus Worksheet Create queries in SQL view in Microsoft Access Commands are typed at prompt in MySQL A Guide to SQL, Seventh Edition

29. Editing SQL Commands Edit commands as you would in a word processor when using Oracle SQL*Plus Worksheet or Access SQL After making edits, click the Execute or Run button With Oracle SQL*Plus or MySQL the on-screen command must be edited to change it A Guide to SQL, Seventh Edition

30. Editing Oracle SQL*Plus In Oracle SQL*Plus you must edit commands one line at a time The most recent command is stored in the command buffer (the buffer) Edit the command in the buffer by using editing commands A Guide to SQL, Seventh Edition

34. Editing MySQL Commands Most recent command is stored in memory area called statement history Edit command in statement history by using specific editing commands A Guide to SQL, Seventh Edition

37. Editing MySQL Commands Press Up arrow key to go to top line Hit Enter key to move to next line if line is correct Use Right and Left arrow keys to move to point needing correction When line is correct hit Enter key If Enter is not hit on a line, that line will not be part of the revised command A Guide to SQL, Seventh Edition

38. Dropping a Table Another way to correct errors is to drop (delete) a table and start over Useful when table is created before errors are discovered Command is followed by the table to be dropped and a semicolon Data is deleted when a table is dropped A Guide to SQL, Seventh Edition

39. Data Types For each column, the type of data must be defined Actual data types vary between SQL programs  there are some common types  CHAR(n), DATE, DECIMAL(p,q), INTEGER, SMALLINT A Guide to SQL, Seventh Edition

40. Nulls A null is used as special value to represent situation when actual value is not known for a column Specify whether to allow nulls in the individual columns Nulls should not be allowed for primary key columns A Guide to SQL, Seventh Edition

41. Implementation of Nulls NOT NULL clause is used in a CREATE TABLE command to exclude the use of nulls in a column Default is to allow null values If a column is defined as NOT NULL, system will reject any attempt to store a null value there A Guide to SQL, Seventh Edition

42. Loading a Table with Data INSERT Command  Adds rows to a table  INSERT INTO followed by the table name  VALUES command follows with specific values in parentheses  Values for character columns are in single quotation marks A Guide to SQL, Seventh Edition

43. The Insert Command A Guide to SQL, Seventh Edition

44. Modifying the INSERT Command To add new rows it is easier to modify previous insert command and execute it Oracle SQL*Plus Worksheet and Access SQL view, select the text, modify and execute Oracle SQL*Plus or MySQL, edit commands manually A Guide to SQL, Seventh Edition

50. The INSERT Command with Nulls Use a special format of INSERT command to enter a null value in a table Identify the names of the columns that accept non- null values, then list only the non-null values after the VALUES command A Guide to SQL, Seventh Edition

51. The INSERT Command with Nulls Enter only non-null values Precisely indicate values you are entering by listing the columns A Guide to SQL, Seventh Edition

52. Viewing Table Data SELECT command is complex A simple version can display all the rows and columns in a table SELECT*FROM followed by the name of the table with the data you want to view As with other SQL commands, it ends with a semicolon A Guide to SQL, Seventh Edition

53. Correcting Errors in the Database UPDATE command is used to update a value in a table DELETE command allows you to delete a record INSERT command allows you to add a record A Guide to SQL, Seventh Edition

56. Saving SQL Commands Allows you to use commands again without retyping Different methods for each SQL implementation you are using  Oracle SQL*Plus and SQL*Plus Worksheet use a script file  Access saves queries as objects  MySQL uses an editor to save text files A Guide to SQL, Seventh Edition

57. Creating the Remaining Tables Execute appropriate CREATE TABLE and INSERT commands Save these commands on your hard drive or a floppy disk for backup A Guide to SQL, Seventh Edition

60. Describing a Table When working with a table, there may not be access to the CREATE TABLE command used for the table Examining the table’s structure will show details about the columns Each DBMS has a method to examine a table’s structure A Guide to SQL, Seventh Edition

61. Describing a Table Oracle SQL*Plus and SQL*Plus Worksheet use DESCRIBE command Access uses the Documenter MySQL uses the SHOW COLUMNS command A Guide to SQL, Seventh Edition

62. Summary Use the CREATE TABLE command to create tables DROP TABLE, INSERT, SELECT, UPDATE and DELETE commands are used to edit tables Display a table’s structure and layout for information A Guide to SQL, Seventh Edition