1. Stored Procedure, Function and Trigger

2. Objectives
Database Programming
Stored Procedure
Function
Trigger

3. 1. Database Programming
1.1 Variables
1.2 Control-of-Flow Tools

4. 1.1 Variables Declare a variable: Assign a value into a variable:
Assign a value into a variable:
Assign a value into a variable in SQL statement:
= price FROM titles WHERE  title_id = 'PC2091'

5. 1.2 Control-of-Flow Tools
1.2.1 BEGIN…END IF…ELSE CASE … WHEN RETURN [n] WHILE PRINT

6. 1.2.1 BEGIN…END Defines a statement block Other Programming Languages:
C#, Java, C: { … }
Pascal, Delphi: BEGIN … END

7. IF…ELSE
Defines conditional and, optionally, alternate execution when a condition is false
IF Boolean_expression 
T-SQL_statement | block_of_statements
[ELSE 
T-SQL_statement | block_of_statements ]
Example:
IF (SELECT ytd_sales FROM titles WHERE title_id = 'PC1035') > 5000
PRINT 'Year-to-date sales are  greater than $5,000 for PC1035.‘

8. 1.2.3 CASE … WHEN CASE input_expression
WHEN  when_expression  THEN result_expression 
[WHEN when_expression  THEN result_expression…n] [ELSE else_result_expression ]
END
Example:
SELECT CASE payterms
WHEN 'Net 30' THEN 'Payable 30 days  after invoice' WHEN 'Net 60' THEN 'Payable 60 days after invoice'  
WHEN 'On invoice' THEN 'Payable upon  receipt of invoice'     
ELSE 'None'    
END as Payment_Terms FROM sales ORDER BY payterms
Other Programming Language
C#, Java: Switch … Case ; VB: Select … Case

9. RETURN [n]
Exits unconditionally of Trigger, Procedure or Function and return a value (if any).

10. WHILE
Repeats a statement (or block) while a specific condition is true
WHILE Boolean_expression 
SQL_statement | block_of_statements
[BREAK] SQL_statement | block_of_statements [CONTINUE]
Example:
WHILE (SELECT AVG(royalty) FROM roysched) < 25
BEGIN
UPDATE roysched SET royalty = royalty * 1.05 IF (SELECT MAX(royalty)FROM roysched) > 27 BREAK
ELSE CONTINUE
END
SELECT MAX(royalty) AS "MAX royalty" 
FROM roysched

11. 1.2.6 PRINT Display message in SQL Query Analyze (Console)
PRINT string
Other Programming Languages:
Java: System.out.print
C#, VB.NET: Console.WriteLine

12. 2. Stored Procedure
2.1 What Is a Stored Procedure? 2.2 Stored Procedure vs. SQL Statement 2.3 Create, update and delete a procedure

13. 2.1 What Is a Stored Procedure?
A stored procedure is a collection of T-SQL statements that SQL Server compiles into a single execution plan.
Procedure is stored in cache area of memory when the stored procedure is first executed so that it can be used repeatedly. SQL Server does not have to recompile it every time the stored procedure is run.
It can accept input parameters, return output values as parameters, or return success or failure status messages.

14. 2.2 Stored Procedure vs. SQL Statement
Creating
Check syntax
Compile
First Time
- Check syntax
- Compile
Execute
Return data
First Time
Execute
Return data
Second Time
- Check syntax
- Compile
Execute
Return data
Second Time
Execute
Return data

15. 2.3 Create, update and delete a procedure
2.3.1 Create a Procedure Update a Procedure Delete a Procedure

16. Create a Procedure
Syntax Example 1 (Without parameters) Example 2 (With parameters) Example 3 (Using RETURN)

17. Syntax
CREATE PROC[EDURE] procedure_name OUTPUT][,...,n]
AS 
T-SQL_statement(s)

18. 2.3.1.2 Example 1 (Without parameters)
CREATE PROC Departments_Members AS
SELECT Dep_Name, COUNT(Emp_ID) NumberOfMember
FROM Departments D, Employees E
WHERE D.Dep_ID = E.Dep_ID
GROUP BY Dep_Name
Run Procedure
Execute Departments_Members

19. 2.3.1.3 Example 2 (With parameters)
CREATE PROC varchar(50) AS
SELECT Dep_Name, COUNT(Emp_ID) NumberOfMember
FROM Departments D, Employees E
WHERE D.Dep_ID = E.Dep_ID and Dep_Name
GROUP BY Dep_Name
Run Procedure
Execute Department_Members ‘Accounting’

20. 2.3.1.4 Example 3 (Using RETURN )
CREATE PROC varchar(10) = null AS is null BEGIN PRINT 'Please enter Employee Code!' RETURN END SELECT * FROM Employees WHERE EMP_EMP_ID = (SELECT EMP_ID FROM Employees WHERE Emp_Code ORDER BY Emp_Name

21. Update a Procedure
ALTER PROC[EDURE] procedure_name data_type] [= default] [OUTPUT] [,...,n] AS t-sql_statement(s)

22. Delete a Procedure
DROP PROCEDURE  procedure_name

23. 3. Function 3.1 What is a Function? 3.2 Scalar functions Example
3.3 Inline Table-valued Functions Example
3.4 Multi-statement Table-Valued Functions Example

24. 3.1 What is a Function? See “What Is a Stored Procedure?” on slide 13
SQL Server supports three types of user-defined functions:
Scalar functions
Inline table-valued functions
Multi-statement table-valued functions

25. 3.2 Scalar functions Example
CREATE FUNCTION Revenue_Day datetime) Returns money AS
BEGIN
money
= sum(sali_Quantity * sali_price)
FROM Sales_Orders s, Sales_Orders_Items si
WHERE s.sal_number = si.sal_number and year(sal_date) =
and month(sal_date) = and day(sal_date)=
END
Use:
select dbo.Revenue_In_Day(GETDATE())

26. 3.3 Inline Table-valued Functions Example
CREATE FUNCTION AveragePricebyItems money = 0.0) RETURNS table AS
RETURN ( SELECT Ite_Description, Ite_Price
FROM Items
WHERE Ite_Price > @price)
Use:
select * from AveragePricebyItems (15.00)

27. 3.4 Multi-statement Table-Valued Functions Example
CREATE FUNCTION AveragePricebyItems2 money = 0.0) table (Description varchar(50) null, Price money null) AS
begin
SELECT Ite_Description, Ite_Price
FROM Items
WHERE Ite_Price > @price
return
end
Use:
select * from AveragePricebyItems2 (15.00)

28. 4. Trigger
4.1 What is a Trigger? 4.2 Creating Syntax 4.3 Disable/Enable syntax 4.4 Deleted and Inserted tables 4.5 Example 4.6 Other Functions

29. 4.1 What is a Trigger?
A trigger is a special type of stored procedure that is executed automatically as part of a data modification.
A trigger is created on a table and associated with one or more actions linked with a data modification (INSERT, UPDATE, or DELETE).
When one of the actions for which the trigger is defined occurs, the trigger fires automatically
Following are some examples of trigger uses:
Maintenance of duplicate and derived data
Complex column constraints
Cascading referential integrity
Complex defaults
Inter-database referential integrity

30. 4.2 Creating Syntax CREATE TRIGGER trigger_name ON <tablename>
<{FOR | AFTER}>
{[DELETE] [,] [INSERT] [,] [UPDATE]} AS
SQL_Statement [...n]

31. 4.3 Disable/Enable syntax
Disable syntax
Disable trigger <trigger_name> on <table_name>
Enable syntax
Enable trigger <trigger_name> on <table_name>

32. 4.4 Deleted and Inserted tables
When you create a trigger, you have access to two temporary tables (the deleted and inserted tables). They are referred to as tables, but they are different from true database tables. They are stored in memory—not on disk.
When the insert, update or delete statement is executed. All data will be copied into these tables with the same structure.
The values in the inserted and deleted tables are accessible only within the trigger. Once the trigger is completed, these tables are no longer accessible.
Inserted Table
Deleted Table
new
old
Insert
Update
Delete

33. 4.5 Example CREATE TRIGGER Print_Update ON Bicycle_Inventory
FOR UPDATE AS
PRINT "The Bicycle_Inventory table was updated"

34. 4.6 Other Functions View contents of trigger
sp_helptext <trigger name>
View number of triggers of a table
sp_helptrigger <table name>

35. ?