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Tworzenie widoków i procedur przechowywanych

Now that Mary can access the TestData database, you may want to create some database objects, such as a view and a stored procedure, and then grant Mary access to them. A view is a stored SELECT statement, and a stored procedure is one or more Transact-SQL statements that execute as a batch.

Views are queried like tables and do not accept parameters. Stored procedures are more complex than views. Stored procedures can have both input and output parameters and can contain statements to control the flow of the code, such as IF and WHILE statements. It is good programming practice to use stored procedures for all repetitive actions in the database.

For this example, you will use CREATE VIEW to create a view that selects only two of the columns in the Products table. Then, you will use CREATE PROCEDURE to create a stored procedure that accepts a price parameter and returns only those products that cost less than the specified parameter value.

To create a view

  • Execute the following statement to create a very simple view that executes a select statement, and returns the names and prices of our products to the user.

    CREATE VIEW vw_Names
   AS
   SELECT ProductName, Price FROM Products;
GO

Test the view

  • Views are treated just like tables. Use a SELECT statement to access a view.

    SELECT * FROM vw_Names;
GO

To create a stored procedure

  • The following statement creates a stored procedure name pr_Names, accepts an input parameter named @VarPrice of data type money. The stored procedure prints the statement Products less than concatenated with the input parameter that is changed from the money data type into a varchar(10) character data type. Then, the procedure executes a SELECT statement on the view, passing the input parameter as part of the WHERE clause. This returns all products that cost less than the input parameter value.

    CREATE PROCEDURE pr_Names @VarPrice money
   AS
   BEGIN
      -- The print statement returns text to the user
      PRINT 'Products less than ' + CAST(@VarPrice AS varchar(10));
      -- A second statement starts here
      SELECT ProductName, Price FROM vw_Names
            WHERE Price < @varPrice;
   END
GO

Test the stored procedure

  • To test the stored procedure, type and execute the following statement. The procedure should return the names of the two products entered into the Products table in Lesson 1 with a price that is less than 10.00.

    EXECUTE pr_Names 10.00;
GO