Database Design

Sections 13 & 16- Introduction to HTML DB SQL editor, Introduction to SQL statements

Marge Hohly 2

Using HTML_DB SQL editor Reference Lab #6 problem 1 You may either type the command into the

SQL editor or use the cut and paste option If you are going to cut/paste the command

copy the command from the word document into NotePad. This will drop out hidden characters.

Next copy the command from the NotePad into the editor

Marge Hohly 3

Enter SQL command

Marge Hohly 4

Display the Table structure

Enter the following command: DESCRIBE MUSIC;

The structure of the table should be shown.

Results on next slide

Marge Hohly 5

Music Table Structure

Marge Hohly 6

Typical error messages The following statement has a spelling error: SELCT *

FROM employees;

The error message is:       ORA-00900: invalid SQL statement

The following statement incorrectly names the table employee instead of employees:

SELECT *FROM employee;

The error message is:       ORA-00942: table or view does not exist

Marge Hohly 7

Insert Data Note the data types for each column Inserting data into the table. Since the table is empty all fields need to be

populated, so column names can be omited INSERT INTO music

VALUES (10,'Marge Hohly','Folk'); This will insert one record into the table Next display the contents of the table to view the data SELECT *

FROM music;

Marge Hohly 8

Resulting Screen

Marge Hohly 9

Inserting Data INSERT INTO tablename (column1, column2,....)

VALUES(value1,value2,...);

Remember character data needs to be enclosed in single quotes.

Marge Hohly 10

SQL DESCRIBE

DESCRIBE <table name>; DESCRIBE employees;

Try the last statement.

Marge Hohly 11

Subset of data WHERE clause

SELECT <column name 1, column name 2, etc.> FROM <table name>WHERE <condition>;

SELECT first_name, last_name, salaryFROM employeesWHERE salary > 5000;

Marge Hohly 12

Insert Data into table

INSERT INTO <table name>VALUES (value 1, value 2, value 3, etc);

INSERT INTO musicVALUES (10,'Marge Hohly','Folk');

Marge Hohly 13

ALTER table structure ALTER TABLE <table name>

ADD (<new_column_name> <data type>);

Try to modify the structure of the MUSIC table

Add a column (which you will misspell) COUNTRI instead of COUNTRY).

Marge Hohly 14

Deleting a column from a table

ALTER TABLE <table name>DROP COLUMN <column_name>;

Now delete the column (COUNTRI) you just added.

Marge Hohly 15

Deleting a row

DELETE from <table name>WHERE <column_name> = 'some value' ;

DELETE from musicWHERE musicid = 10;

DELETE from musicWHERE type = ‘Folk’;

Marge Hohly 16

Database Facts Currently 20% of the world's data resides in relational

DBMSs. In the next two years, databases are expected to

grow larger than 100 terabytes. A database this big would be able to store 100,000 copies of the Encyclopedia Britannica or 200,000 hours of music or about 10 billion web pages.

The top 10 world's largest databases using the Oracle DBMS are: France Telecom, 29.2TB -- a communications company

(a TB is a terabyte equivalent to 1,000 gigabytes) Amazon.com with, 13 TB -- selling books and

merchandise The Claria Corporation,12TB -- Internet behavioral

marketing company tracking Internet user behavior

Marge Hohly 17

HTML DB SQL editor The SQL course will use the three following sets of database tables for

examples and practice exercises.

Oracle tables: COUNTRIES, REGIONS, DEPARTMENTS, EMPLOYEES, JOBS, JOB_HISTORY AND JOB_GRADES

DJs on Demand database tables: D_CDS, D_PACKAGES, D_TYPES, D_THEMES, D_CLIENTS, D_VENUES, D_SONGS, D_TRACK_LISTINGS, D_PARTNERS, D_EVENTS, D_PLAY_LIST_ITEMS, D_JOB_ASSIGNMENTS

Global Fast Foods database tables: F_CUSTOMERS, F_REGULAR_MENUS, F_PROMOTIONAL_MENUS, F_SHIFTS, F_STAFFS, F_FOOD_ITEMS, F_ORDERS, F_ORDER_LINES, F_SHIFT_ASSIGNMENTS

Print out these tables for your reference when using the HTML DB editor These tables are available on the Student Resource web page for this

class

Marge Hohly 18

Review the tables There are six properties of tables in a relational

database: Property 1: Entries in columns are single-valued. Property 2: Entries in columns are of the same kind. Property 3: Each row is unique. Property 4: Sequence of columns is insignificant. Property 5: Sequence of rows is insignificant. Property 6: Each column has a unique name.

Marge Hohly 19

Categories of SQL Statements Data manipulation language (DML) statements

Begin with INSERT, UPDATE, DELETE, or MERGE Used to modify the table by entering new rows, changing existing rows, or

removing existing rows.

Data definition language (DDL) statements set up, change, and remove data structures from the database. The keywords CREATE, ALTER, DROP, RENAME, and TRUNCATE begin DDL

statements.

Transaction control (TCL) statements are used to manage the changes made by DML statements. Changes to the data are executed using COMMIT, ROLLBACK, and

SAVEPOINT. TCL changes can be grouped together into logical transactions.

Data control language (DCL) keywords GRANT and REVOKE are used to give or remove access rights to

the database and the structures within it.

Marge Hohly 20

16.2.6 Questions1. The Fast Foods database consists of how many tables? ____ tables

2. How is the F_SHIFTS table related to the F_STAFFS table?

3. What are the names of the columns in the F_CUSTOMERS table?

4. How many rows of data have been entered in the F_PROMOTIONAL_MENUS table?

5. In the F_FOOD_ITEMS table, column _________ is a foreign-key column. What table and column is this key referencing?

6. List the primary key to foreign key relationships required to go from the F_SHIFTS table to the F_REGULAR_MENUS table.

7. Which table(s) contain null values?

Marge Hohly 21

KEYWORD, CLAUSE, STATEMENT Throughout this course, the words keyword,

clause, and statement are used as follows: A keyword refers to an individual SQL element.

For example, SELECT and FROM are keywords. A clause is a part of a SQL statement.

SELECT employee_id, last_name, .... is a clause.

A statement is a combination of two or more clauses.SELECT *FROM employees;

is a SQL statement.

Marge Hohly 22

Selection vs. Projection SELECT salary

FROM employeesWHERE last_name like ‘Smith’;

Selection (row) Projection (column)

ID First_name Last_name salary

10 John Doe 4000

20 Jane Jones 3000

30 Sylvia Smith 5000

40 Hai Nguyen 6000

Marge Hohly 23

What is null? If a row lacks the data value for a particular

column, that value is said to be null, or to contain a null. A null isa value that is unavailable, unassigned, unknown, or inapplicable.

A null is not the same as zero. Zero is a number.

A null is not a space. Space is a character.

Marge Hohly 24

Arithmetic Expressions Create expressions

with number and date data by using arithmetic operators. Operator Description

+ Add

- Subtract

* Multiply

/ Divide

Marge Hohly 25

Operator Precedence Operator Precedence

Multiplication and division take priority over addition and subtraction.

Operators of the same priority are evaluated from left to right.

Parentheses are used to force prioritized evaluation and to clarify statements.

Remember: Please excuse my dear aunt Sally

() ^ * / + -

Marge Hohly 26

Rewrite in order of precedence You want to calculate the annual salary if the

employee received $100 raise each month Revise the following statement in the correct

order of precedence to get the desired results Run each example in the editor SELECT last_name, salary, 12*salary+100

FROM employees;

Marge Hohly 27

Null Values in Arithmetic Expressions SELECT last_name, salary, commission_pct,

salary*commission_pctFROM employees;

SALARY COMMISSION_PCT SALARY*COMMISSION_PCT

2500 (null) (null)

10500 .2 2100

11000 .3 3300

8600 .2 1720

7000 .15 1050

(null) (null) (null)

Marge Hohly 28

Practice SELECT *

FROM d_songs; SELECT id, title, duration, artist, type_code

FROM d_songs; SELECT id, title, artist,

FROM d_songs; SELECT last_name, salary, salary – 300

FROM employees; SELECT last_name, salary, salary * 1.05

FROM employees;

Marge Hohly 29

Column Alias Renames a column heading Is useful in naming columns of

derived values Immediately follow the column name Uses optional AS keyword between

the column name and alias Required double quotation marks if it

contains spaces or special characters or is case sensitive

Marge Hohly 30

Using Aliases SELECT last_name name, salary AS Salary, salary*12

“Annual Salary”FROM employees;

NAME SALARY Annual Salary

Whalen 4400 52800

Hartstein 13000 156000

Fay 6000 72000