1. Lab 2: Retrieving Data from the Database
CISB224 02A, 02B
Semester I, 2009/2010
College of Information Technology, Universiti Tenaga Nasional

2. The SELECT Statement
Syntax SELECT select_list FROM table_source [WHERE search_condition] [GROUP BY group_by_expression] [HAVING search_condition] [ORDER BY order_by_expression]
A query must be comprised of the SELECT and FROM clauses
All other clauses are optional (denoted by [ ])
College of Information Technology, Universiti Tenaga Nasional

3. The SELECT Clause
Syntax SELECT [ALL | DISTINCT] { * | {column_name | expression} [[AS] column_alias] } [,…n]
This is called the select list!
College of Information Technology, Universiti Tenaga Nasional

4. The SELECT Clause – cont.
The select list must be comprised (denoted by {}) of one or more of the following (denoted by [,…n])
* - a “shortcut” that means all columns in the table
{column_name|expression} – your choice (denoted by |) of either a column from the table or an expression that evaluates to a value e.g. a string, number, date, etc.
College of Information Technology, Universiti Tenaga Nasional

5. The SELECT Clause – cont.
Example 1
SELECT Name, Title
FROM emp
Display the employees’ names and their job titles.
Note!
SQL is not case-sensitive
Write clauses on separate lines to enhance readability
College of Information Technology, Universiti Tenaga Nasional

6. The SELECT Clause – cont.
A column alias is used to:
Replace the heading of a table column in the result
Provide a heading to a column formed from an expression
Use ‘ ’ to enclose a column alias when it is made up of two or more words
College of Information Technology, Universiti Tenaga Nasional

7. The SELECT Clause – cont.
Example 2
SELECT Name Employee_Name, Title ‘Job Title’
FROM emp
Display the employees’ last names with the heading Employee_Name and their job titles with the heading ‘Job Title’.
College of Information Technology, Universiti Tenaga Nasional

8. The SELECT Clause – cont.
The DISTINCT argument is used when you do not want to view duplicate rows in the result
ALL is the default argument and need not be specified
College of Information Technology, Universiti Tenaga Nasional

9. The SELECT Clause – cont.
Example 3
Display the State where customers are located.
SELECT DISTINCT State
FROM Cust
College of Information Technology, Universiti Tenaga Nasional

10. The SELECT Clause – cont.
Arithmetical expressions in SQL:
may be formed from columns of numeric type and/or constants
are governed by the normal evaluation rules
2 * (3 + 4) = ?
Operation
Operator
Addition +
Subtraction -
Multiplication *
Division /
The addition operator, +, may also be used for string concatenation
College of Information Technology, Universiti Tenaga Nasional

11. The SELECT Clause – cont.
Example 4
SELECT Name, BuyingPrice + BuyingPrice * 25 / 100
FROM Product
Display the products’ names and their new price as 25% more than the current price
College of Information Technology, Universiti Tenaga Nasional

12. The SELECT Clause – cont.
Example 5
SELECT ID + ‘ ’ + Name as ‘Employee Detail’
FROM emp
Display the employees’ full name as one column.
College of Information Technology, Universiti Tenaga Nasional

13. The ORDER BY Clause
Syntax [ORDER BY {order_by_expression [ASC|DESC]} [,…n]]
College of Information Technology, Universiti Tenaga Nasional

14. The ORDER BY Clause – cont.
The order_by_expression may be:
A column name
May or may not be in the select list
A column alias
Expressions other than the above
The position of the expression in the select list
College of Information Technology, Universiti Tenaga Nasional

15. The ORDER BY Clause – cont.
ASC
On characters - alphabetical order
On numbers - increasing order
On dates – chronological order
DESC – opposite of the above!
College of Information Technology, Universiti Tenaga Nasional

16. The ORDER BY Clause – cont.
Example 6
SELECT StartDate, Name, ID
FROM emp
ORDER BY StartDate DESC
Display all employees’ start date, ID and name. Sort the results by start date and name, both in descending order.
College of Information Technology, Universiti Tenaga Nasional

17. The ORDER BY Clause – cont.
Example 7
Display all employees’ start date along with ID and name as one column i.e. ‘E60002, Zarina Majid. Sort the results by start date and name, both in descending order.
College of Information Technology, Universiti Tenaga Nasional

18. The ORDER BY Clause – cont.
Example 7 – cont.
SELECT StartDate, ID + ‘, ’ + Name AS Emp_Detail
FROM emp
ORDER BY StartDate DESC, 2 DESC
ORDER BY StartDate DESC, Emp_Detail DESC
ORDER BY StartDate DESC, ID + ‘, ’ + Name DESC
College of Information Technology, Universiti Tenaga Nasional

19. The WHERE clause Syntax [WHERE column_name operator expression]
This syntax is simplified for the purpose of today’s (very gentle) introduction to the WHERE clause 
College of Information Technology, Universiti Tenaga Nasional

20. The WHERE clause – cont. Comparison Operators = Is equal to <>
Is not equal to
<
Is less than
<=
Is less than or equal to
>
Is greater than
>=
Is greater than or equal to
College of Information Technology, Universiti Tenaga Nasional

21. The WHERE clause – cont. Example 8
SELECT Name, Salary, Dept
FROM emp
WHERE Dept=‘Admin’
Display the names, salary and department for all employees in Admin department.
College of Information Technology, Universiti Tenaga Nasional

22. The WHERE clause – cont. Example 9
SELECT *
FROM Inventory
WHERE AmountInStock < ReorderPoint
Display all products whose amount in stock have fallen below the reorder point.
College of Information Technology, Universiti Tenaga Nasional

23. The WHERE clause – cont. Logical Operators BETWEEN
Between two values, inclusive
ReorderPointBETWEEN 25 AND 50 IN
In a list of values
State IN (Johor, Perak, KL)
College of Information Technology, Universiti Tenaga Nasional

24. The WHERE clause – cont. Example 10
SELECT Name, Salary, Dept
FROM emp
WHERE Salary BETWEEN 1200 AND 2000
Display the names of all employees whose salary is between 1200 and 2000
College of Information Technology, Universiti Tenaga Nasional

25. The WHERE clause – cont. Example 11
SELECT State
FROM Cust
WHERE State IN (Johor, Perak, KL)
Display all suppliers who are located in Johor, Perak and KL.
College of Information Technology, Universiti Tenaga Nasional