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Stored Procedures & User Defined Functions MacDonald Ch. 23

Stored Procedures & User Defined Functions MacDonald Ch. 23. MIS 424 Professor Sandvig. Today. Stored Procedures Store SQL statements on DB User Defined Functions (UDF) Database Transactions Rollback. Stored Procedures. So far: Putting SQL queries in .NET code

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Stored Procedures & User Defined Functions MacDonald Ch. 23

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  1. Stored Procedures & User Defined FunctionsMacDonald Ch. 23 MIS 424 Professor Sandvig

  2. Today • Stored Procedures • Store SQL statements on DB • User Defined Functions (UDF) • Database Transactions • Rollback

  3. Stored Procedures • So far: • Putting SQL queries in .NET code • Use command object to pass to database • Alternative: • Stored procedures • Store SQL query on database • Call query from .aspx page or business object

  4. Stored Procedures • Benefits of SP: • Reusability • Call same SP from many locations in code • Loose coupling • Create clear separation between code & data • Reduces dependencies • Changes in data source do not affect code • N-Tier Programming • Diagram (Source: Microsoft)

  5. Benefits of Stored Procedures • Division of duties • Programmers vs. database admin • Security • Set permissions on procedures • Users see only data accessible via procedure

  6. Benefits of Stored Procedures • Efficiency • SQL compiled • Execution plan saved • Execute complex procedures • Triggers • Multiple SQL statements • Programming languages • Transact-SQL • .NET languages

  7. Disadvantages • More code, greater abstraction • Not fully supported by all databases • MySQL • Recently added • Limited • Access • Store simple SQL statements

  8. Creating • Visual Studio

  9. Creating

  10. Syntax & Example Example: • GetTitlesSP.aspx • See handout

  11. Views & Functions • Views • “Virtual” tables • No data, definition only • Retrieve data only • May include data from several tables • No parameters • Benefits: • Hide table details • Set permissions

  12. User Defined Functions • Functions (user defined functions) • Retrieve only • May use parameters • May call from SPs, other functions, SQL commands • Benefits • Reusability • Hide complexity

  13. User Defined Functions • Creating in Visual Studio

  14. User Defined Functions • Syntax Create FUNCTION dbo.GetProductCategories ( @ProductID int ) RETURNS TABLE AS RETURN Select c.CatLabel FROM tblCategories c, tblProductCategories p where c.CategoryID = p.CategoryID AND p.ProductID = @ProductID sql = "select * from dbo.GetProductCategories(16) order by CatLabel";

  15. Transactions • Many transactions have dependency • Bank transfer • Remove $$ from one account • Add to another • On-line purchase • Charge credit card • Ship item • Item out-of-stock?

  16. Transactions If one task fails: • Prior transactions are rolled back • Supported by most commercial databases • Not mySQL • Database keeps a log of transaction • Easy to use • Example: source, output

  17. Summary • Advanced Data Techniques • Stored Procedures • Parameters • Transactions • Goal: • Modularity • Reusability • Robust

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