Tài liệu, ebook Cơ Sở Dữ Liệu

Summary EER model Limitations of Basic Concepts of the ER Model Enhanced-ER (EER) Model Concepts Subclasses and Superclasses Specialization and Generalization Specialization / Generalization Hierarchies, Lattices and Shared Subclasses Categories Formal Definitions of EER Model Database Design Modeling Tools Next week: Relational model & ...

36 trang | Chia sẻ: vutrong32 | Ngày: 19/10/2018 | Lượt xem: 1060 | Lượt tải: 0

Summary What is ER Model? And Why? Overview of Database Design Process Example COMPANY Database ER Model Concepts ER Diagram Alternative Diagrammatic Notations (UML) Problems with ER Models Next week: EER Reading: [1] Chapter 4 [2] Chapter 12

54 trang | Chia sẻ: vutrong32 | Ngày: 19/10/2018 | Lượt xem: 1541 | Lượt tải: 0

TRANSFORM CLASS DIAGRAM TO RELATIONAL DATABASE SCHEMA In general, the transformation of class diagram to relational schema is similar to that of EER to relational schema, except some specific issues. 1.  Transform a class in class diagram to a table 2.  Transform an attribute of a class to a table column. 3.  In case a class does not have a...

45 trang | Chia sẻ: vutrong32 | Ngày: 19/10/2018 | Lượt xem: 1042 | Lượt tải: 0

A multidatabase system is a special distributed database system where one node may be running relational database system under Unix, another may be running object-oriented system under Window and so on. A transaction may run in a distributed fashion at multiple nodes. In this execution scenario the transaction commits only when all these multiple n...

36 trang | Chia sẻ: vutrong32 | Ngày: 19/10/2018 | Lượt xem: 1221 | Lượt tải: 0

The set of rules which must be followed for producing serializable schedule are The lock compatibility must adhered to. The root of the tree must be locked first, in any mode. A node N can be locked by a transaction T in S or IX mode only if the parent node is already locked by T in either IS or IX mode. A node N can be locked by T in X, IX, or...

48 trang | Chia sẻ: vutrong32 | Ngày: 19/10/2018 | Lượt xem: 1070 | Lượt tải: 0

Potential problem with lower isolation levels (cont.): Phantoms: New rows being read using the same read with a condition. A transaction T1 may read a set of rows from a table, perhaps based on some condition specified in the SQL WHERE clause. Now suppose that a transaction T2 inserts a new row that also satisfies the WHERE clause condition of ...

54 trang | Chia sẻ: vutrong32 | Ngày: 19/10/2018 | Lượt xem: 1156 | Lượt tải: 0

Oracle DBMS V8 Rule-based query optimization: the optimizer chooses execution plans based on heuristically ranked operations. (Currently it is being phased out) Cost-based query optimization: the optimizer examines alternative access paths and operator algorithms and chooses the execution plan with lowest estimate cost. The query cost is calcula...

66 trang | Chia sẻ: vutrong32 | Ngày: 19/10/2018 | Lượt xem: 1124 | Lượt tải: 0

Difference between B-tree and B+-tree In a B-tree, pointers to data records exist at all levels of the tree In a B+-tree, all pointers to data records exists at the leaf-level nodes A B+-tree can have less levels (or higher capacity of search values) than the corresponding B-tree

26 trang | Chia sẻ: vutrong32 | Ngày: 19/10/2018 | Lượt xem: 1054 | Lượt tải: 0

Advantages of SANs are: Flexible many-to-many connectivity among servers and storage devices using fiber channel hubs and switches. Up to 10km separation between a server and a storage system using appropriate fiber optic cables. Better isolation capabilities allowing nondisruptive addition of new peripherals and servers. SANs face the problem ...

32 trang | Chia sẻ: vutrong32 | Ngày: 19/10/2018 | Lượt xem: 1245 | Lượt tải: 0

Execution Engine The execution engine has the responsibility for executing each of the steps in the chosen query plan. The execution engine interacts with most of the other components of the DBMS, either directly or through the buffers. It must get the data from the database into buffers in order to manipulate that data. It needs to interact w...

22 trang | Chia sẻ: vutrong32 | Ngày: 19/10/2018 | Lượt xem: 1071 | Lượt tải: 0