This document compares scripts versus stored procedures in SQL and outlines key capabilities and concepts of stored procedures. Stored procedures can contain multiple SQL statements and have more capabilities than scripts. Parameters allow sending data into and returning data from stored procedures. Stored procedures use programming constructs like variables, conditional logic, loops, and error handling to perform complex actions on the database. Transactions allow grouping statements to commit or rollback as a single unit of work.

1. CIS-282

2. Scripts v. Stored Procedures
 Script: Text file of SQL commands
 Stored Procedure: SQL commands stored in database
itself
 SPROC’s have more capabilities than a script

3. BATCH
 Batch is a logical group of SQL statements
 Run-time error will halt execution only of FURTHER
steps
 Can break up multiple steps using GO
 Not available in all tools
 GO causes editing tool to send statements to that point
for execution
 GO isn’t sent to SQL Server

4. Format of SPROC’s
CREATE PROCEDURE <name>
<parameter list>
AS
<instructions to execute>

5. EXECUTE
 EXEC(cute) statement
OR
 EXEC(cute) stored procedure name
 Statement or sproc runs in it’s own scope
 Can’t ‘share’ variables directly
 User’s security rules apply
 Can’t be used in User Defined Function (UDF)

6. Uses of Stored Procedures
 For returning data (select)
 For editing data
 For calculations

7. Parameters
 Method for sending data into and from a stored
procedure
 INPUT parameters are values sent in
 OUTPUT parameters are values returned
 Must have a holding space (variable) for the returned data
 Defined before start of procedure (AS)

8. Declaring Parameters
 Include name and datatype
 Default value is optional
 Without a default value, parameter is required
 Direction is optional (input is default)
 An output parameter must have direction specified

9. Sample Input Parameter
CREATE PROC upFindStudent
@SID char(9)
AS
SELECT *
FROM Persons
Where SchoolID=@SID

10. Sample Output Parameter
CREATE PROC upFindStudentID
@First varchar(25),
@Last varchar(35),
@SID char(9) OUTPUT
AS
SELECT @SID=SchoolID
FROM Students_T
Where @First=Firstname and
@Last=Lastname

11. Return Values
 Result of stored procedure indicates success or failure
 Non-zero value indicates a problem
 Must be an integer
 Different from an output parameter
 Output parameter is about data
 RETURN <value>
 Causes immediate exit

12. Variables
 Create using DECLARE
 Need to start with ‘@’
 Can use SQL data types or custom data types
DECLARE @StudentName varchar(50)

13. Variable Assignment
 SET is usually used similar to procedural language
SET @Var=value
 SELECT is usually used when getting a value from a
query
SELECT @Var=Sum(PossiblePoints) FROM Assignments

14. Decision Making
 SQL supports two structures for branching:
 IF
 CASE
 Both structures are similar to other languages (IF …
THEN, SELECT CASE)
 Both structures tend to have specific places where used

15. IF Blocks
 IF … ELSE
 No end if
 Need to use Begin/End if have more than one
instruction to execute
IF StartDate < EndDate
Begin
…
End
ELSE

16. Simple Case Statement
 CASE
 Similar to SELECT CASE
 Compares one value to different cases
CASE Category
WHEN ‘pop_comp’ THEN ‘Popular Computing’
WHEN ‘mod_cook’ THEN ‘Modern Cooking’
END

17. Searched CASE
 No test expression
 Each WHEN has a boolean test
CASE
WHEN Points >= 90 THEN ‘A’
WHEN Points < 90 AND Extra > 0
THEN ‘A’
END

18. Looping (While)
 Typically used with a CURSOR
 Cursor data type allows a table to be stored in memory
and each row/field to be accessed
 BREAK allows early exit from loop
 CONTINUE forces control to start of loop
 Working with sets is preferred over loops (SQL is
about sets)

19. Finding Identity Values
 When need to find the value used to identify the last
row added
 @@Identity
 Scope_Identity
 Ident_Current

20. @@Identity
 System variable, created/maintained automatically
 Returns the last identity value used as a result of
INSERT or SELECT INTO
 Not limited to current scope; may not get correct value
 Returns Null if operation failed or a value wasn’t
generated
 Returns last number created if multiple inserts occur
(i.e. SELECT INTO)

21. Scope_Identity()
 Return the last identity values generated in any table
in the current session.
 Returns values inserted only within the current scope
 Not affected by other operations.

22. Ident_Current()
 Not limited by scope and session;
 Limited to a specified table (table name specified as an
argument value).

23. @@Rowcount
 System variable, created/maintained automatically
 Number of rows returned or affected by the last
statement
 0 (zero) is often used as a logical test
 If no records found for where clause, notify system or
process

24. Errors
 Errors can occur because of SQL statement
 Invalid syntax, or data type
 Errors can also reflect business rules
 Data doesn’t match requirements

25. @@Error
 System variable, created/maintained automatically
 Value set after each SQL statement;
 0 (zero) means statement was successful
 Number other than zero is typically a specific error
 Can store value in variable and test

26. Try/Catch
 Similar to .Net languages
 Need to include BEGIN/END
BEGIN TRY
<code>
END TRY
BEGIN CATCH
<error handling code>
END CATCH

27. Raise Error
 Used to send information to calling program
 Syntax:
RaisError (Message string OR Message ID, Severity,
State)
 Severity – <14 information; 15-19 warning or user
can correct; 20+ fatal
 State – way to differentiate problems if needed;
typically use 1
 RAISERROR (50001,16,1)

28. Error Message
 Message ID or String
 Use ID if have custom or TSQL error to use
 Use String for ‘on the fly’ message
 Stored Error Messages are server-specific
 Can add message to server
 ID Number must be greater than 50000

29. Custom Error Messages
 Messages can include a parameter with % to allow
addition to message
 ‘D’ – signed integer
 ‘O’ – unsigned octal
 ‘P’ – pointer
 ‘S’ – string
 ‘U’ – unsigned integer
 ‘X’ or ‘x’ – unsigned hexadecimal

30. Severity & State
 1 – 18: Informational (range can vary – not exact)
 11 – 16 typically raise error at client
 19 – 25: Severe error
 20+ is fatal error and connection will terminate
 State is ‘ad hoc’ and can help if same error happens in
multiple places
 Range of 1 – 127

31. Sample Error Message
 RaisError(‘Operation cannot be completed because
field %s cannot be null’,1,1,’fieldname’)

32. Transactions
 Provides method for canceling an operation
 Can restore rows, columns to original state in event of
error or business logic failure
 Use when changes will either be committed or
discarded in entirety

33. ACID
 Atomicity: All of the changes will be accepted or none of
the changes will be accepted
 Consistency: Data is either in its original or changed state
 Isolation: If multiple transactions occur, data is never
available in an intermediate state
 Durability: Once finished, all changes are complete and
changes can only be done by another transaction/unit of
work

34. Using A Transaction
 Begin Tran: Identifies the start
 Commit Tran: Write changes
 Rollback Tran: Cancel changes
 Be sure to issue a Commit or Rollback
 Connection Stays Open Until Transaction is terminated

35. Locking & Concurrency
 Locking allows a transaction to ensure that it can
rollback
 Prevents other operations from changing that data
 Concurrency refers to multiple actions running against
database at the same time
 What happens if you want to change data I’m working
with?

36. Sample Locking Levels
 Database
 Table
 Extent (memory)
 Page (subset of extent)
 Key
 Row

37. Cursors
 Processing based on each row
 not set operations
 Declare @Cursor Cursor
 Set @Cursor = Cursor For (select statement)
 Open @Cursor
 Fetch Next From @Cursor into (variables matching
field list in select)

38. Using a Cursor
Declare @Students Cursor
Set @Cursor = Cursor For (Select FirstName, LastName From
Students)
Open @Students
While @@Fetch_Status = 0
Begin
Fetch Next From @Students Into @First, @Last
Print @First + ‘ ‘+ @Last
End
Close @Students
Deallocate @Students

39. @@Fetch_Status
 0 success;
 -1 failed (read record outside recordset);
 -2 missing record (eg. someone else deleted)