Sql Functions And Procedures
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SQL procedures and functions allow reusable groups of SQL statements to be created and executed. Procedures can contain multiple statements and take parameters, while functions return a single value. Both can be created, altered, and deleted using SQL commands like CREATE, ALTER, and DROP. Functions are preferable to procedures because they are more organized, allow return values, and avoid using temporary tables.
Sql Functions And Procedures
- 1. 12SQL SERVER: SQLFUNCTIONS AND PROCEDURES
- 2. SQL ProceduresWhat is an SQL Procedure? An SQL Procedure contains a group of sql statements which solve a common purpose. Syntax:Consider a simple SQL Procedure:Create proc printProcedureAsPrint ‘Hello World’goCreate proc <procedureName>As…. Statements…Print is a command in SQL Server 2008. It is used to print a string on the screen.NOTE: The SQL Procedures that we learn here are stored in the system by the DBMS. They are hence known as stored procedures
- 3. Altering stored proceduresHow to alter a SQL stored procedure? A Stored procedure can be altered using the alter proc command.Syntax:Consider a simple SQL Procedure:Alter proc printProcedureAsPrint ‘New Hello World’goAlter proc<procedureName>As…. New Statements…
- 4. Executing ProceduresThe Main advantage of using a stored procedure is its reusability, i.e., a procedure can be called any time that it needs to be executed.An SQL procedure can be executed using the exec command:Exec <ProcedureName>Example: Create proc printProcedureAsPrint ‘New Hello World’GoExec printProcedureOUTPUT:New Hello World
- 5. Procedure ParametersA Procedure, like a C or C++ Procedure(function) can take up input parameters and produce return values.Output Parameters (Returned Values)SQL ProcedureInput ParametersA Procedure with Input Parameters:Create proc hellop@info1 int= 1,@info2 intAsPrint @info1+@info2Calling a Procedure with parameters:Exec proc hellop 3,2
- 6. Procedure ParametersCalling a Procedure with parameters:Exec proc hellop 3,2Here, the value ‘3’ over-rides the default value. If a paramater does not have a default value defined for it, then the DBMS requires the user to pass a value for it before execution.Eg: exec proc hellop 1: will return an error as the second parameter is not assigned any value.
- 7. Procedure ParametersOutput Parameters:A Procedure can have output parameters also. The Output parameters are specified by the keyword output.Consider a procedure to add two numbers:Create proc adder@num1 int =0,@num2 int =0,AsDeclare @num3 int= @num1 + @num2;Print @num3;GoExecuting the procedure: exec proc adder 3,4 Output: 7A Procedure can also return a value as: return <value>NOTEThe Data members in SQL (@num1) resemble the variables in c/c++. But there is a big difference: They can’t be altered directly.Eg: @num1 = @num1 +1 Is invalid. The values are assigned at the time of their declaration only.
- 8. Procedure ParametersUsing the Output parameters:CREATE PROC Sales @CustomerIDint, @AccNumvarchar(10) OUTPUTASSELECT @AccNum = AccNum FROM Sales.Customer WHERE CustomerID = @CustomerID;GOCalling a procedure with return values: DECLARE @AccNumvarchar(10);EXEC GetCustomerAccountNumber, @AccNum OUTPUT;PRINT @AccNum;
- 9. Deleting proceduresThe SQL statement to drop/delete a procedure is:Drop proc <procedureName>Example:Drop proc addNumbers;Go;
- 10. FunctionsWhat is a Function?A Function is a set of sql statements which aim to accomplish the same task.How is a function different from a procedure? A Function is more clear, organized and structured
- 11. It is easy to modify
- 12. It is easy to handle return values than in procedures. In procedures, a temporary table might be necessary to carry a return value and join it with an existing table. This becomes unnecessary if functions are used instead.FunctionsUser-defined functions are routines written using Transact-SQL or the Dot NET Common Language Runtime. Transact-SQL:Transact-SQL (T-SQL) is an extension to SQL, created by Microsoft' and Sybase.Transact-SQL enhances SQL with these additional features: Enhancements to DELETE and UPDATE statements
- 14. Local variables
- 15. Various support functions for string processing, date processing, mathematics, etc.Dot Net Common Language Runtime(CLR):It is a run-time environment which runs code and provides services that make development process much easier.
- 16. Functions are betterThe Advantages of using functions in SQL Server 2008:
- 17. FunctionsThe SQL Syntax for creating a function resembles that of a procedure:Create function <functionName>(argumentList) Returns <returnValueType> As Begin …statements… Return <returnValue> EndGoLet us look into some examples.
- 18. FunctionsA Sample function:Consider a function that takes two numbers and finds their sum:Create function adder(@num1 int,@num2 int)Returns intAsBeginDeclare @num3 int;Set @num3 = @num1+@num2;Return @num3;EndgoNote that the SET keyword is used to change the value of a variableCalling the function:The Prefix dbo instructs the DBMS that you are the database ownerPrint dbo.adder(2,4)go
- 19. Deleting FunctionsThe SQL statement to drop/delete a function is similar to that of a procedure:Drop function <procedureName>Example:Drop function addNumbers;Go;
- 21. Creating Procedures
- 22. Modifying existing procedures
- 23. Deleting procedures
- 24. Functions
- 25. Creating functions
- 26. Modifying existing functions
- 27. Deleting functionsVisit more self help tutorialsPick a tutorial of your choice and browse through it at your own pace.The tutorials section is free, self-guiding and will not involve any additional support.Visit us at www.dataminingtools.net