This document provides an overview of basic T-SQL programming concepts including declaring variables, IF/ELSE statements, WHILE loops, and CASE expressions. It defines local variables using DECLARE, demonstrates assigning values using SET and SELECT, and shows how to conditionally execute code blocks using IF and IF/ELSE statements. Examples are also provided for WHILE loops, including using the BREAK and CONTINUE keywords, and the syntax for simple and searched CASE expressions is described. Sample databases, tables, and data are included for examples.

1. Basics of T-SQL programming
Declaring variables and Parameters
1

2. • A local variable is defined using the DECLARE statement.
• The name of the local variable needs to start with the @ symbol
as the first character of its name.
Example: DECLARE @Count INT
• More than one variable can be defined with a single DECLARE
statement with a comma
Example: DECLARE @Count INT, @X INT, @Y INT, @Z
• A local variable is initially assigned a NULL value.
• A value can be assigned to a local variable by using the SET or
SELECT statement.
• Using SET:-
DECLARE @Count INT
SET @Count = 1
• Using SELECT statement to initialize the value of a local
variable with the value returned from a select that fetch the total
number of rows in the customer table.
declare @rowcount int
select @rowcount=(selectcount(*)from customer
print @rowcount
2

3. • An example that returns all the Customers records in the sales
database where the customer’s address column is equal to ‘Bahir
Dar’
declare @myaddress varchar(50)
set @myaddress='bahir dar'
select*from customer where [address]=@myaddress
Example
declare @var1 int,@var2 float,@var3 int,@sum int
set @var1=10
set @var2=20
set @var3=30
set @sum=@var1+@var2+@var3
print @sum
N.B.you can also use select to assign and to
display
3

4. IF ... ELSE statement
• T-SQL has the IF statement to help with allowing different code to be
executed based on the results of a condition.
• Format one:
IF <condition> <then code to be executed >
• Format two:
IF <condition> <then code to be executed >
ELSE < else code to be executed >.
• If a block of code is used then it will need to be enclosed in a BEGIN
and END statement.
Declare @x int
set @x = 29
if @x = 29 print 'The number is 29'
if @x = 30 print 'The number is 30'
• Now the condition statement can also contain a SELECT statement.
• The SELECT statement will need to return value or set of values that
can be tested. 4

5. Example
if(selectcount(*)from customer)<20
print'Number of customer is less than 20’
• If a SELECT statement is used the statement needs to be enclosed in parentheses.
parentheses.
Example
if (select count(*) from Student
where fname like '[A-D]%') > 0
print 'A-D Students are Found ‘
Example
if db_name() = 'master'
begin
Print 'We are in the Master Database'
Print ‘ ’
Print 'So whatever code you execute must be done carefully'
End
else if db_name() = ‘Library'
begin
Print 'We are in the test Library database ’
Print 'So Enjoy' 5

6. •Suppose we want to determine whether to update or
add a record to the Customer table in the Sales
database.
if exists(select * from customer where
Customer_ID = 'C-150')
Print 'Need to update'
else
Print 'Need to add new record'
Example
if exists(select*from customer
where customer_id='c-100')
print'record is found'
else
print'record is not found'
6

7. Example
declare @x int
set @x=-80;
if(@x>0)
begin
print'number is positive'
end
else if(@x<0)
begin
print'number is negative'
end
else
print'number is zero'
7

8. WHILE Loop With CONTINUE and BREAK Keywords
• Syntax:
WHILE Boolean_expression
{ sql_statement | statement_block | BREAK | CONTINUE }
{sql_statement | statement_block}
• BREAK: Causes an exit from the innermost WHILE loop.
• CONTINUE: Causes the WHILE loop to restart, ignoring any statements
after the CONTINUE keyword.
Example
DECLARE @intFlag INT
SET @intFlag = 1
WHILE (@intFlag <=5)
BEGIN
PRINT @intFlag
SET @intFlag = @intFlag + 1
END
8

9. Example : Usage of WHILE Loop with BREAK keyword
DECLARE @intFlag INT
SET @intFlag = 1
WHILE (@intFlag <=5)
BEGIN
PRINT @intFlag
SET @intFlag = @intFlag + 1
IF @intFlag = 4
BREAK;
END
GO
• Example
declare @start int
set @start=65
while(@start<=90)
begin
print char(@start)
set @start+=1
end 9

10. Example
WHILE (SELECT AVG(ListPrice) FROM Production.Product) < 300
BEGIN
UPDATE Production.Product
SET ListPrice = ListPrice * 2
SELECT MAX(ListPrice) FROM Production.Product
IF (SELECT MAX(ListPrice) FROM Production.Product) > 500
BREAK
ELSE
CONTINUE
END
• In the above example, if the average list price of a product
is less than $300, the WHILE loop doubles the prices
selects the maximum price.
• If the maximum price is less than or equal to $500,
the WHILE loop restarts and doubles the prices again.
• This loop continues doubling the prices until the
maximum price is greater than $500, and then exits
the WHILE loop. 10

11. CASE… When expressions
•Evaluates a list of conditions and returns one of multiple
possible result expressions.
•The CASE expression has two formats:
- The simple CASE expression compares an expression to
a set of simple expressions to determine the result.
- The searched CASE expression evaluates a set of
Boolean expressions to determine the result. Within a
SELECT statement, the searched CASE expression
allows for values to be replaced in the result set based on
comparison values.
Syntax for The simple CASE expression:
CASE input_expression
WHEN when_expression THEN result_expression [ ...n
]
[ELSE else_result_expression] 11

12. Example
declare @x int
set @x=20
select
case
when @x>0 then'x is positive'
when @x<0 then'x is negative'
else'x is zero'
endas'My result 1’
Example
declare @my_variable int
set @my_variable=2
select
case @my_variable
when 1 then'the number is one'
when 2 then'the number is two'
else'the number is unknown'
endas'My result 2’
Example
select first_name,
case [address]
when'bahir dar'then'your address is bahir dar'
when'Addis Abeba'then'your address is addis'
when'Gonder'then'your address is gondar'
else'address unknown'
endas'your address'
from customer
orderby first_name
12

13. Example
select first_name,last_name,
case sex
when'm'then'you are male'
when'f'then'you are female'
else'unknown'
endas'Gender'
from customer
orderby first_name
Example
select first_name,last_name,
case
when sex='m'then'you are male'
when sex='f'then'you are female'
else'unknown'
endas'Gender'
from customer
orderby first_name
13

14. Exercise
1. Using if …Else statement write a T-
SQL program to print the grade of a
student. Assume that a student table
has (StudId, FN,LN, Age, mark) and
write A if the mark is above 80, B if the
mark is between 79 and 60 and C if is
less than 60
2. Use while… loop write a T-SQL
program to find the factorial of a
number
3. Describe the Syntax of CASE……When14

15. Use the following sample database for your example
create database sales
use sales
create table customer
(
Customer_ID varchar(50)not null,
First_Name varchar(200)not null,
Last_Name varchar(200) not null,
Sex char(1),
[Address] varchar(255),
primary key(Customer_ID)
)
create table Product
(
Product_ID char(200),
Product_Name varchar(255),
purchase_Price money,
Acquired_Date date,
product_price money,
Manufacturer varchar(255),
primary key(Product_ID)
)
create table [Order]
(
Order_ID int identity(1,1),
Product_ID char(200),
Customer_ID varchar(50),
Order_Date date,
primary key(Order_ID),
foreign key(Product_ID)references
Product(Product_ID),
foreign key(Customer_ID)references
customer(Customer_ID)
)
15

16. use sales
insert into customer
values('C-100','Birhanu','Bogale','M','Gonder'),
('C-101','Asnakech','Worku','F','Addis Abeba'),
('C-102','Chala','Debele','M','Nazrete'),
('C-103','Dereb', 'Asmamaw','M','Dangla'),
('C-104','Eshetu','Amare','M','Bahir Dar'),
('C-105','Girma', 'Moges','M','Addis Abeba'),
('C-106','Haymanot', 'Degu','F','Mekele'),
('C-107','Alem', 'Tefera','F','Bahir Dar'),
('C-108','Zebider', 'Yetagesu','F','Desse'),
('C-109','Habtam', 'Tegabu','F','Gonder'),
('C-110','Fikir', 'Ashenafi','M','Bahir Dar'),
('C-111','Alex', 'Amanu','M','Bahir Dar'),
('C-112','Ahmed', 'Nuredin','M','Debre Markos'),
('C-113','Aysha', 'Tesfa','F','Debre Tabor'),
('C-114','Befkadu', 'Honelgn','M','Gonder')
16

17. use sales
insert into product
values('P-100','Stationary',1500,'2013-01-01',2500,'Beuty company'),
('P-101','Hard disk',2700,'2015-03-05',2500,'SeaGate'),
('P-102','Monitor',700,'2015-03-05',1100,'Dell'),
('P-103','Stationary',4000,'2014-07-04',5900,'Sanitation'),
('P-104','Printer',5000,'2013-04-06',2400,'Dell'),
('P-105','Keyboard',350,'2012-02-04',500,'Microsoft'),
('P-106','Computer',5000,'2011-08-02',7400,'Sony'),
('P-107','Laptop',10000,'2013-03-05',13000,'Toshiba'),
('P-108','Camera',1500,'2014-05-01',2600,'Webcam company'),
('P-109','Plotter',5300,'2013-01-02',6800,'SAMSUNG'),
('P-110','Laptop',15000,'2013-01-02',23000,'Lenovo')
17

18. use sales
insert into [order]
values ('P-108','C-104','2013-03-06'),
('P-108','C-114','2014-05-01'),
('P-100','C-106','2015-08-01'),
('P-103','C-106','2011-02-08'),
('P-109','C-110','1999-01-07'),
('P-110','C-114','1980-04-01'),
('P-102','C-100','2015-01-08'),
('P-104','C-100','2012-03-05'),
('P-101','C-101','2013-04-07'),
('P-105','C-102','2014-09-07'),
('P-106','C-103','1996-01-05'),
('P-107','C-105','2014-03-07'),
('P-104','C-108','2015-02-04'),
('P-102','C-109','2012-02-04'),
('P-109','C-111','2014-03-09'),
('P-100','C-112','2015-04-01'),
('P-105','C-113','2013-08-07'),
('P-110','C-114','1993-07-02'),
('P-104','C-107','2012-05-07') 18