1. SQL – Structured Query Language

2. Relational Database Operators
Relational algebra determines
table manipulations
Key operators
SELECT
PROJECT
JOIN
Other operators
UNION
INTERSECT
DIFFERENCE
PRODUCT
DIVIDE

3. Union
Combines all rows
Figure 2.5

4. Intersect
Yields rows that appear in both tables
Figure 2.6

5. Difference
Yields rows not found in other tables
Figure 2.7

6. Product
Yields all possible pairs from two tables
Figure 2.8

7. Select
Yields a subset of rows based on specified criterion
Figure 2.9

8. Project
Yields all values for selected attributes
Figure 2.10

9. Join Information from two or more tables is combined Figure 2.11

10. Natural Join Process
Links tables by selecting rows with common values in common attribute(s)
Three-stage process
Product creates one table
Select yields appropriate rows
Project yields single copy of each attribute to eliminate duplicate columns

11. Other Joins
EquiJOIN
Links tables based on equality condition that compares specified columns of tables
Does not eliminate duplicate columns
Join criteria must be explicitly defined
Theta JOIN
EquiJOIN that compares specified columns of each table using operator other than equality one
Outer JOIN
Matched pairs are retained
Unmatched values in other tables left null
Right and left

12. Divide Requires user of single-column table and two-column table
Figure 2.17

13. Data Dictionary and System Catalog
Provides detailed account of all tables found within database
Metadata
Attribute names and characteristics
System catalog
Detailed data dictionary
System-created database
Stores database characteristics and contents
Tables can be queried just like any other tables
Automatically produces database documentation

14. Introduction to SQL Ideal database language
Create database and table structures
Perform basic data management chores (add, delete, and modify)
Perform complex queries to transform data into useful information
SQL is the ideal DB language
Data definition language (DDL)
Data manipulation language (DML)

15. DDL vs. DML examples Name DDL: Data Definition Language
DML: Date Manipulation Language
Purpose
Defines Structure of Database and Database Objects
Manipulates the Data housed in the tables
Add
Create table: creates a new table
Insert Into: adds a new record to a table
Change
Alter table: modifies the tables structure (add a column, change a datatype, add constraint, etc.)
Update: changes the values of an attribute in a record
Remove
Drop table: deletes the table from the database
Delete: deletes a record from a table

16. Most Common Data Types Data Type Data Type Description CHAR(n)
fixed length column can contain any printable characters.
If the data entered into CHAR field < length of field, field is padded with spaces.
maximum length of CHAR column = 200.
e.g: a state abbreviation - CHAR(2) since it is always 2 characters long.
VARCHAR2(n)
variable length column with a fixed length. If the length of the data is less than the maximum length of the field, then the field is not padded with spaces.
maximum length of the column = 2000.
e.g: a customer’s first name - VARCHAR2(35) since name length is variable.
NUMBER
Integer and real values occupying up to 40 spaces.
INTEGER
Same as number, but no decimals.
DATE
contains a date and time between the 1st of January 4712 BC to the 31st of December 4712 AD.
standard date format: DD-MMM-YY (i.e. 01-JAN-99)
Any other format will require input mask.

17. Creating Table Structure
CREATE TABLE <table name> (<attribute1 name and attribute1 characteristics, attribute2 name and attribute2 characteristics, attribute3 name and attribute3 characteristics, primary key designation, foreign key designation and foreign key requirement>);
Null vs. Not Null (can the field be left blank when data entered NOTE: null <> 0
Check constraints – show acceptable values for attribute and/or default value.
Data types and size
Column Names

18. Drop – table or column Delete table from database:
Drop table <tablename> cascade constraints
e.g. drop table student cascade constaints
Delete column from database
Alter table <tablename> drop column <column name>
e.g. alter table student drop column student_lastname

19. Using Domains Domain is set of permissible values for a column
Definition requires:
Name
Data type
Default value
Domain constraint or condition
CREATE DOMAIN <domain_name> AS DATA_TYPE [DEFAULT <default_value>]
[CHECK (<condition>)]

20. SQL Integrity Constraints and Data Anomolies
Entity integrity - enforced automatically with PRIMARY KEY constraint
Referential integrity - enforced FOREIGN KEY constraint
Other specifications to ensure conditions met:
ON DELETE RESTRICT
ON UPDATE CASCADE

21. Data Anomalies, Redundacy, and constraints
Modification
Insertion
Deletion
ON UPDATE CASCADE
PRIMARY KEY constraint
ON DELETE RESTRICT

22. Alter, Add, and Modify ALTER - changes table structure
ADD - adds column
MODIFY - changes column characteristics
ALTER TABLE <table name> ADD (<column name> <new column characteristics>);
ALTER TABLE <table name> MODIFY (<column name> <new column characteristics>);

23. Data Manipulation Commands
Common SQL DML Commands
Table 5.3

24. Enters data into a table
Data Entry and Saving
Enters data into a table
Saves changes to disk
INSERT INTO <table name>
VALUES (attribute 1 value, attribute 2 value, … etc.);
COMMIT <table names> ;

25. Listing Table Contents and Other Commands
Allows table contents to be listed
UPDATE command makes data entry corrections
ROLLBACK command restores database back to previous condition if COMMIT hasn’t been used
DELETE command removes table row
SELECT <attribute names> FROM <table names>;

26. Queries Creating partial listings of table contents
SELECT <column(s)> FROM <table name> WHERE <conditions>;
Table 5.4
Mathematical Operators

27. Examples Mathematical operators
Mathematical operators on character attributes
Mathematical operators on dates
SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODE
FROM PRODUCT
WHERE V_CODE <> 21344;
SELECT P_CODE,P_DESCRIPT,P_ONHAND,P_MIN,P_PRICE FROM PRODUCT WHERE P_CODE < ‘1558-QWI’;
SELECT P_DESCRIPT,P_ONHAND,P_MIN,P_PRICE,PINDATE FROM PRODUCT WHERE P_INDATE >= ‘01/20/2002’;

28. Computed Columns
New columns can be created through valid computations or formulas
Formulas may contain mathematical operators
May contain attributes of any tables specified in FROM clause
Alias is alternate name given to table or column in SQL statement
SELECT P_DESCRIPT,P_ONHAND,P_PRICE,P_ONHAND*P_PRICE
AS TOTVALUE
FROM PRODUCT;

29. Operators
SELECT *
FROM PRODUCT WHERE V_CODE = OR V_CODE = 24288;
Logical: AND, OR, NOT
Rules of precedence
Conditions within parenthesis executed first
Boolean algebra
Special
BETWEEN - defines limits
IS NULL - checks for nulls
LIKE - checks for similar string
IN - checks for value in a set
EXISTS - opposite of IS NULL

30. Drop column and update Dropping a column
Update (add new data to a column)
ALTER TABLE VENDOR DROP COLUMN V_ORDER;
UPDATE PRODUCT SET P_SALECODE = ‘2’ WHERE P_CODE = ‘1546-QQ2’;
Table 5.5

31. Arithmetic Operators – Rules of Precedence
Arithmetic operators and rules of precedence
Table 5.5

32. Advanced Data Management Commands (con’t.)
Copying parts of tables
Deleting a table from database
Primary and foreign key designation
INSERT INTO <receiving table> <receiving table’s column names> SELECT <column names of the columns to be copied> FROM <contributing table name>;
DROP TABLE PART;
ALTER TABLE LINE
ADD PRIMARY KEY (INV_NUMBER, LINE_NUMBER)
ADD FOREIGN KEY (INV_NUMBER) REFERENCES INVOICE
ADD FOREIGN KEY (PROD_CODE) REFERENCES PRODUCT;

33. Aggregate Function Operations Count, Max and Min
SELECT COUNT(DISTINCT V_CODE) FROM PRODUCT;
SELECT COUNT(DISTINCT V_CODE) FROM PRODUCT WHERE P_PRICE <= 10.00;
SELECT MIN(P_PRICE) FROM PRODUCT;
SELECT P_CODE, P_DESCRIPT, P_PRICE FROM PRODUCT WHERE P_PRICE = MAX(P_PRICE);

34. Aggregate Function Operaters Sum/ Avg
SELECT SUM(P_ONHAND * P_PRICE) FROM PRODUCT;
SELECT P_DESCRIPT, P_ONHAND, P_PRICE, V_CODE FROM PRODUCT WHERE P_PRICE > (SELECT AVG(P_PRICE) FROM PRODUCT) ORDER BY P_PRICE DESC;

35. Order by ORDER BY <attributes> ORDER BY <attributes> DESC
Ordering a listing
Results ascending by default
Descending order uses DESC
Cascading order sequence
ORDER BY <attributes>
ORDER BY <attributes> DESC
ORDER BY <attribute 1, attribute 2, ...>

36. Distinct SELECT DISTINCT V_CODE FROM PRODUCT;
Listing unique values
DISTINCT clause produces list of different values
SELECT DISTINCT V_CODE
FROM PRODUCT;

37. Group by/ Having Grouping data Creates frequency distributions
Only valid when used with SQL arithmetic functions
HAVING clause operates like WHERE for grouping output
SELECT P_SALECODE, MIN(P_PRICE) FROM PRODUCT_2 GROUP BY P_SALECODE;
SELECT V_CODE,COUNT(DISTINCT(P_CODE)),AVG(P_PRICE)
FROM PRODUCT_2
GROUP BY V_CODE
HAVING AVG(P_PRICE) < 10;

38. Joins Joining database tables Data retrieved from more than one table
SELECT PRODUCT.P_DESCRIPT, PRODUCT.P_PRICE,
VENDOR.V_NAME, VENDOR.V_CONTACT,
VENDOR.V_AREACODE, VENDOR.V_PHONE FROM PRODUCT, VENDOR WHERE PRODUCT.V_CODE = VENDOR.V_CODE;