Transcript null

Database Design
Sections 13 & 16
- Introduction to HTML DB SQL editor,
Introduction to SQL statements
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
2
Enter SQL command
Marge Hohly
3
Display the Table structure
 Enter the following command:
 DESCRIBE MUSIC;
 The structure of the table should be
shown.
 Results on next slide
Marge Hohly
4
Music Table Structure
Marge Hohly
5
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
6
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
7
Resulting Screen
Marge Hohly
8
Inserting Data
 INSERT INTO tablename (column1, column2,....)
VALUES(value1,value2,...);
 Remember character data needs to be
enclosed in single quotes.
Marge Hohly
9
SQL DESCRIBE
 DESCRIBE <table name>;
 DESCRIBE employees;
Try the last statement.
Marge Hohly
10
Subset of data WHERE clause
 SELECT <column name 1, column
name 2, etc.>
FROM <table name>
WHERE <condition>;
 SELECT first_name, last_name, salary
FROM employees
WHERE salary > 5000;
Marge Hohly
11
Insert Data into table
 INSERT INTO <table name>
VALUES (value 1, value 2, value 3,
etc);
 INSERT INTO music
VALUES (10,'Marge Hohly','Folk');
Marge Hohly
12
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
13
Deleting a column from a table
 ALTER TABLE <table name>
DROP COLUMN <column_name>;
 Now delete the column (COUNTRI)
you just added.
Marge Hohly
14
Deleting a row
 DELETE from <table name>
WHERE <column_name> = 'some
value' ;
 DELETE from music
WHERE musicid = 10;
 DELETE from music
WHERE type = ‘Folk’;
Marge Hohly
15
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
16
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
17
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
18
Categories of SQL Statements

Data manipulation language (DML) statements



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.


Begin with INSERT, UPDATE, DELETE, or MERGE
Used to modify the table by entering new rows, changing existing rows, or
removing existing rows.
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
19
16.2.6 Questions
1.
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
20
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
21
Selection vs. Projection
 SELECT salary
FROM employees
WHERE 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
22
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
23
Arithmetic Expressions
 Create expressions
with number and
date data by using
arithmetic
Operator
operators.
+
Description
Add
-
Subtract
*
Multiply
/
Divide
Marge Hohly
24
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
25
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
26
Null Values in Arithmetic
Expressions
 SELECT last_name, salary, commission_pct,
salary*commission_pct
FROM 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
27
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
28
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
29
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
Marge Hohly
30