1. How to: SQL
By: Sam Loch

2. Goal To retrieve data from and insert data into a relational database
Product
ProductID
ProductName
Price
InventoryLevel
Order-Product
OrderProductID
OrderID
ProductID
Quantity
Order
OrderID
CustomerID
OrderDate
ShippingInstructions
Customer
CustomerID
FirstName
LastName
Phone
Address

3. How to Accomplish Our Goal
Structured Query Language (SQL)
Using SQL we can
Retrieve data from a database
Insert data into a database
Update data in a database
Delete data in a database
Add and delete tables form a database
Combine tables in a database

4. Creating a Database Define the database Create tables
Define columns within these tables and choose their data types
Each table needs a Primary Key
Some tables will need Foreign Key’s to communicate with other tables in the database

5. Creating a Database (2) CREATE statements Text Description
These can be used to create a table within a database
Example:
CREATE TABLE db_name.table_name (
ColumnName1 datatype NOT NULL,
ColumnName2 datatype NULL,
PRIMARY KEY (KeyName));
Text
Description
NULL/NOT NULL
Defines whether the field can be empty (NULL) or whether it cannot (NOT NULL)
Primary Key’s cannot be NULL
datatype
The data-type of the column.

6. Creating a Database (3) Order OrderID CustomerID OrderDate
Another Example:
CREATE TABLE salesdb.Order (
OrderID INT NOT NULL,
CustomerID INT NOT NULL,
OrderDate DATE NULL,
ShippingInstructions VARCHAR(45) NULL,
PRIMARY KEY (OrderID));
Order
OrderID
CustomerID
OrderDate
ShippingInstructions

7. Data Types Each column can contain a different type of data
The data type of each column must be specified when it is created
A few data types:
Data type
Description
Examples
INT
Integer
4, 62, -20
DECIMAL(p,s)
Decimal. Example: decimal(6,3) is a number that has 3 digits after the decimal and 6 digits total ( )
6.5, ,
VARCHAR(x)
String of any characters with a maximum length of x
‘Howdy’,
‘She sells seashells by the sea shore’
DATETIME, DATE
Date and time, or just Date
' :43:00', ' '
BOOLEAN
Boolean value
0,1

8. Foreign Keys Product ProductID ProductName Price InventoryLevel
The Foreign Key in one table connects that table to a Primary key in another table.
CREATE TABLE salesdb.`Order-Product` (
OrderProductID INT NOT NULL,
OrderID INT NULL,
ProductID INT NULL,
Quantity INT NULL,
PRIMARY KEY (OrderProductID),
FOREIGN KEY (OrderID) REFERENCES salesdb.Order(OrderID)
FOREIGN KEY (ProductID) REFERENCES salesdb.Product(ProductID)
Product
ProductID
ProductName
Price
InventoryLevel
Order-Product
OrderProductID
OrderID
ProductID
Quantity
ProductID is a foreign key in the Order-Product table, and the primary key in the Product table.

9. Deleting Tables DROP TABLE db_name.table_name;
EX: DROP TABLE salesdb.Product;

10. Altering the Data in a Table
Adding a column: ALTER TABLE db_name.table_name ADD COLUMN column_name datatype (NULL or NOT NULL); Deleting a column: DROP COLUMN column_name; Changing a column: CHANGE COLUMN old_column_name new_column_name datatype (NULL or NOT NULL);

11. Altering the Data in a Table (2)
Examples:
ALTER TABLE salesdb.Product
ADD COLUMN Color VARCHAR(10) NULL;
DROP COLUMN Color;
CHANGE COLUMN Color
Version VARCHAR(20) NULL;
Adds “Color” column to Product table
Deletes “Color” column to Product table
Changes “Color” column from Product table to “Version” and changes character limit from 10 to 20

12. Adding a Row to a Table INSERT INTO db_name.table_name
(ColumnName1, ColumnName2, ColumnName3)
VALUES (Value1, Value2, Value3);
Example:
INSERT INTO salesdb.Customer
(CustomerID, FirstName, LastName, , Phone, Address)
VALUES (2003, ‘Kit’, ‘Fisto’, .com’, , ‘560 Lois Lane Pittsburgh, PA’)
CustomerID
FirstName
LastName
Phone
Address
1999
Johnny
Bravo
1624 N. 18th Street Philadelphia, PA
2000
Dwight
Shrute
12 Farm Street Scranton, PA
2001
Patches
O‘Houlihan
34 Legend Lane Lancaster, PA
2002
Eric
Foreman
1919 S. 19th Street Philadelphia, PA
2003
Kit
Fisto
560 Lois Lane Pittsburgh, PA

13. The Price of the Shake Weight was changed to 99.99
Changing a Row
UPDATE db_name.table_name
SET ColumnName1 = Value1, ColumnName2 = Value2
WHERE condition;
Example:
UPDATE salesdb.Product
SET ProductName = ‘Shake Weight’, Price = 99.99
WHERE ProductID = 1341;
ProductID
ProductName
Price
1341
Shake Weight
99.99
1342
The Claw
29.99
1343
SHAM WOW
4.99
The Price of the Shake Weight was changed to 99.99

14. Deleting a Row DELETE FROM db_name.table_name WHERE condition;
Example:
DELETE FROM salesdb.Product
WHERE ProductID = 1738;

15. Retrieving Data From a Database
SELECT statements
SELECT statements are used to retrieve data from a database
EX:
SELECT column_name(s)
FROM db_name.table_name;

16. SELECT statements
CustomerID
FirstName
LastName
Phone
Address
1999
Johnny
Bravo
1624 N. 18th Street Philadelphia, PA
2000
Dwight
Shrute
12 Farm Street Scranton, PA
2001
Patches
O‘Houlihan
34 Legend Lane Lancaster, PA
2002
Eric
Foreman
1919 S. 19th Street Philadelphia, PA
2003
Kit
Fisto
560 Lois Lane Pittsburgh, PA
If you had a customer table and wanted to see the first and last names of all of the customers you would type:
SELECT FirstName, LastName
FROM salesdb.Customer
This would return:
FirstName
LastName
Johnny
Bravo
Dwight
Shrute
Patches
O‘Houlihan
Eric
Foreman
Kit
Fisto

17. Retrieving All Columns in a Table
SELECT * FROM salesdb.Customer
CustomerID
FirstName
LastName
Phone
Address
1999
Johnny
Bravo
1624 N. 18th Street Philadelphia, PA
2000
Dwight
Shrute
12 Farm Street Scranton, PA
2001
Patches
O‘Houlihan
34 Legend Lane Lancaster, PA
2002
Eric
Foreman
1919 S. 19th Street Philadelphia, PA
2003
Kit
Fisto
560 Lois Lane Pittsburgh, PA

18. Retrieving Values To retrieve only unique values:
SELECT DISTINCT Price
FROM salesdb.Product;
To retrieve certain records only
SELECT * FROM salesdb.Product WHERE Price = 99.99;
SELECT * FROM salesdb.Product WHERE Price > 5;

19. WHERE Clause Operator Description = Equal to > Greater than >=
The following is a list of operators that can be used in the WHERE Clause:
Operator
Description =
Equal to
>
Greater than
>=
Greater than or equal to
<
Less than
<=
Less than or equal to
<>
Not equal to

20. Sorting Results of a Select Statement
SELECT * FROM salesdb.Customer WHERE CustomerID >= 2000 ORDER BY FirstName;
CustomerID
FirstName
LastName
Phone
Address
2000
Dwight
Shrute
12 Farm Street Scranton, PA
2002
Eric
Foreman
1919 S. 19th Street Philadelphia, PA
2003
Kit
Fisto
560 Lois Lane Pittsburgh, PA
2001
Patches
O‘Houlihan
34 Legend Lane Lancaster, PA

21. ORDER BY Ascending (ASC) and Descending (DESC)
SELECT * FROM salesdb.Product ORDER BY Price ASC; ORDER BY Price DESC;
ProductID
ProductName
Price
1343
Shake Weight
4.99
1342
The Claw
29.99
1341
SHAM WOW
99.99
ProductID
ProductName
Price
1341
Shake Weight
99.99
1342
The Claw
29.99
1343
SHAM WOW
4.99

22. Other SQL Functions COUNT() – Returns the number of rows
MAX() – Returns the largest value
MIN() – Returns the smallest value
SUM() – Returns the sum
AVG() – Returns the average value

23. Fun With Functions
ProductID
ProductName
Price
1341
Shake Weight
99.99
1342
The Claw
29.99
1343
SHAM WOW
4.99
Price
99.99
SELECT MAX(Price) FROM salesdb.Product; SELECT COUNT(ProductID) FROM salesdb.Product; SELECT MIN(Price) FROM salesdb.Product; SELECT SUM(Price) FROM salesdb.Product; SELECT AVG(Price) FROM salesdb.Product; 3
Price
4.99
Price
134.97
Price
44.99

24. SELECTing From Multiple Tables
To SELECT from multiple tables you must join the tables with WHERE
Example:
SELECT * FROM salesdb.Customer, salesdb.Order
WHERE Customer.CustomerID = Order.CustomerID;
This Returns:
Customer.CustomerID
FirstName
LastName
Phone
Address
OrderID
OrderDate
Order.CustomerID
2000
Dwight
Shrute
12 Farm Street Scranton, PA
102
1002
2002
Eric
Foreman
1919 S. 19th Street Philadelphia, PA
103
1003
2003
Kit
Fisto
560 Lois Lane Pittsburgh, PA
104
1004
2001
Patches
O‘Houlihan
34 Legend Lane Lancaster, PA
105
1005

25. JOIN Syntax SELECT * Return all the columns from both tables
SELECT * FROM salesdb.Customer, salesdb.Order WHERE Customer.CustomerID = Order.CustomerID;
SELECT *
Return all the columns from both tables
FROM salesdb.Customer, salesdb.Order
The two tables to be joined
WHERE Customer.CustomerID = Order.CustomerID
Only choose records where the CustomerID exists in both tables

26. Summary Text Description NULL/NOT NULL
Defines whether the field can be empty (NULL) or whether it cannot (NOT NULL)
Primary Key’s cannot be NULL
datatype
The data-type of the column.
Use CREATE statements to create a table
Use DROP TABLE to delete a table
Use ALTER TABLE to change the data in a table
ADD COLUMN
DROP COLUMN
CHANGE COLUMN
Use INSERT INTO to add a row
Use UPDATE and SET to change
a row
Use DELETE FROM to delete a
row
Data type
Description
Examples
INT
Integer
4, 62, -20
DECIMAL(p,s)
Decimal. Example: decimal(6,3) is a number that has 3 digits after the decimal and 6 digits total ( )
6.5, ,
VARCHAR(x)
String of any characters with a maximum length of x
‘Howdy’,
‘She sells seashells by the sea shore’
DATETIME, DATE
Date and time, or just Date
' :43:00', ' '
BOOLEAN
Boolean value
0,1

27. Summary(2) Use SELECT statements to retrieve data from a database
SELECT * selects all data from
COUNT() – Returns the number of rows
MAX() – Returns the largest value
MIN() – Returns the smallest value
SUM() – Returns the sum
AVG() – Returns the average value