Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Entity–attribute–value model wikipedia , lookup
Microsoft Access wikipedia , lookup
Oracle Database wikipedia , lookup
Open Database Connectivity wikipedia , lookup
Ingres (database) wikipedia , lookup
Extensible Storage Engine wikipedia , lookup
Concurrency control wikipedia , lookup
Microsoft Jet Database Engine wikipedia , lookup
Relational model wikipedia , lookup
Clusterpoint wikipedia , lookup
Physical Database Design University of California, Berkeley School of Information Management and Systems SIMS 257: Database Management 9/25/2001 SIMS 257: Database Management Review • Database Design Process • Normalization 9/25/2001 SIMS 257: Database Management Database Design Process Application 1 External Model Application 2 Application 3 Application 4 External Model External Model External Model Application 1 Conceptual requirements Application 2 Conceptual requirements Application 3 Conceptual requirements Conceptual Model Logical Model Application 4 Conceptual requirements 9/25/2001 SIMS 257: Database Management Internal Model Normalization • Normalization theory is based on the observation that relations with certain properties are more effective in inserting, updating and deleting data than other sets of relations containing the same data • Normalization is a multi-step process beginning with an “unnormalized” relation – Hospital example from Atre, S. Data Base: Structured Techniques for Design, Performance, and Management. 9/25/2001 SIMS 257: Database Management Normal Forms • • • • • • First Normal Form (1NF) Second Normal Form (2NF) Third Normal Form (3NF) Boyce-Codd Normal Form (BCNF) Fourth Normal Form (4NF) Fifth Normal Form (5NF) 9/25/2001 SIMS 257: Database Management Normalization No transitive dependency between nonkey attributes All determinants are candidate keys - Single multivalued dependency 9/25/2001 BoyceCodd and Higher SIMS 257: Database Management Functional dependencyof nonkey attributes on the primary key - Atomic values only Full Functional dependencyof nonkey attributes on the primary key Unnormalized Relations • First step in normalization is to convert the data into a two-dimensional table • In unnormalized relations data can repeat within a column 9/25/2001 SIMS 257: Database Management Unnormalized Relation Patient # Surgeon # 145 1111 311 Surg. date Patient Name Jan 1, 1995; June 12, 1995 John White Patient Addr Surgeon 15 New St. New York, NY 243 1234 467 2345 189 Jan 8, 1996 Charles Brown 4876 145 Nov 5, 1995 Hal Kane 5123 145 May 10, 1995 Paul Kosher Charles Field 10 Main St. Patricia Rye, NY Gold Dogwood Lane Harrison, David NY Rosen 55 Boston Post Road, Chester, CN Beth Little Blind Brook Mamaronec k, NY Beth Little 6845 243 Apr 5, 1994 Dec 15, 1984 Ann Hood Hilton Road Larchmont, Charles NY Field 9/25/2001 Postop drug Drug side effects Gallstone s removal; Beth Little Kidney Michael stones Penicillin, Diamond removal none- Apr 5, 1994 May 10, 1995 Mary Jones Surgery SIMS 257: Database Management rash none Eye Cataract removal Thrombos Tetracyclin Fever is removal e none none Open Heart Surgery Cholecyst ectomy Gallstone s Removal Eye Cornea Replacem ent Eye cataract removal Cephalosp orin none Demicillin none none none Tetracyclin e Fever First Normal Form Patient # Surgeon # Surgery DatePatient Name Patient Addr Surgeon Name 1111 145 01-Jan-95 John White 1111 311 12-Jun-95 John White 15 New St. New York, NY 15 New St. New York, NY 1234 243 05-Apr-94 Mary Jones 10 Main St. Rye, NY 1234 467 10-May-95 Mary Jones 2345 4876 5123 6845 6845 9/25/2001 189 145 145 243 243 Charles 08-Jan-96 Brown 10 Main St. Rye, NY Dogwood Lane Harrison, NY 05-Nov-95 Hal Kane 55 Boston Post Road, Chester, CN 05-Apr-94 Ann Hood 15-Dec-84 Ann Hood Hilton Road Larchmont, NY Drug adminSide Effects Charles Field Gallstone s removal Kidney stones removal Eye Cataract removal Patricia Gold Thrombos is removal none none David Rosen Open Heart Surgery none Beth Little Cholecyst ectomy Demicillin Beth Little Michael Diamond Blind Brook Mamaronec 10-May-95 Paul Kosher k, NY Beth Little Hilton Road Larchmont, NY Surgery Penicillin rash none none Tetracyclin e Fever Cephalosp orin Charles Field Gallstone s Removal none Eye Cornea Replacem Tetracyclin ent e Charles Field Eye cataract removal SIMS 257: Database Management none none none Fever none Second Normal Form Patient # 1111 1234 2345 4876 5123 6845 9/25/2001 Patient Name Patient Address 15 New St. New John White York, NY 10 Main St. Rye, Mary Jones NY Charles Dogwood Lane Brown Harrison, NY 55 Boston Post Hal Kane Road, Chester, Blind Brook Paul Kosher Mamaroneck, NY Hilton Road Ann Hood Larchmont, NY SIMS 257: Database Management Second Normal Form Surgeon # Surgeon Name 145 Beth Little 189 David Rosen 243 Charles Field 311 Michael Diamond 467 Patricia Gold 9/25/2001 SIMS 257: Database Management Second Normal Form Patient # Surgeon # Surgery Date 1111 1111 1234 1234 2345 4876 9/25/2001 Surgery Drug Admin Side Effects 145 Gallstones 01-Jan-95 removal Kidney Penicillin rash 311 stones 12-Jun-95 removal none none 243 Eye Cataract 05-Apr-94 removal Tetracycline Fever 467 Thrombosis 10-May-95 removal 189 Open Heart 08-Jan-96 Surgery Cephalospori n none 145 Cholecystect 05-Nov-95 omy Demicillin none none none none none 5123 145 6845 243 6845 243 Gallstones 10-May-95 Removal Eye cataract 15-Dec-84 removal Eye Cornea 05-Apr-94 Replacement SIMS 257: Database Management none none Tetracycline Fever Third Normal Form Patient # Surgeon # Surgery Date 9/25/2001 Surgery Drug Admin 1111 145 1111 311 01-Jan-95 Gallstones removal Kidney stones 12-Jun-95 removal 1234 243 05-Apr-94 Eye Cataract removal Tetracycline 1234 467 10-May-95 Thrombosis removal 2345 189 08-Jan-96 Open Heart Surgery Cephalosporin 4876 145 05-Nov-95 Cholecystectomy Demicillin 5123 145 10-May-95 Gallstones Removal none 6845 243 none 6845 243 15-Dec-84 Eye cataract removal Eye Cornea 05-Apr-94 Replacement SIMS 257: Database Management Penicillin none none Tetracycline Third Normal Form Drug Admin 9/25/2001 Side Effects Cephalosporin none Demicillin none none none Penicillin rash Tetracycline Fever SIMS 257: Database Management Most 3NF Relations are also BCNF Patient # 1111 1234 2345 4876 5123 6845 9/25/2001 Patient Name Patient Address 15 New St. New John White York, NY 10 Main St. Rye, Mary Jones NY Charles Dogwood Lane Brown Harrison, NY 55 Boston Post Hal Kane Road, Chester, Blind Brook Paul Kosher Mamaroneck, NY Hilton Road Ann Hood Larchmont, NY SIMS 257: Database Management Fourth Normal Form • Any relation is in Fourth Normal Form if it is BCNF and any multivalued dependencies are trivial • Eliminate non-trivial multivalued dependencies by projecting into simpler tables 9/25/2001 SIMS 257: Database Management Fifth Normal Form • A relation is in 5NF if every join dependency in the relation is implied by the keys of the relation • Implies that relations that have been decomposed in previous NF can be recombined via natural joins to recreate the original relation. 9/25/2001 SIMS 257: Database Management Normalization • Normalization is performed to reduce or eliminate Insertion, Deletion or Update anomalies. • However, a completely normalized database may not be the most efficient or effective implementation. • “Denormalization” is sometimes used to improve efficiency. 9/25/2001 SIMS 257: Database Management Denormalization • Usually driven by the need to improve query speed • Query speed is improved at the expense of more complex or problematic DML (Data manipulation language) for updates, deletions and insertions. 9/25/2001 SIMS 257: Database Management Downward Denormalization Before: Customer ID Address Name Telephone After: Order Order No Date Taken Date Dispatched Date Invoiced Cust ID 9/25/2001 Customer ID Address Name Telephone Order Order No Date Taken Date Dispatched Date Invoiced Cust ID Cust Name SIMS 257: Database Management Upward Denormalization Order Order No Date Taken Date Dispatched Date Invoiced Cust ID Cust Name Order Price Order Order No Date Taken Date Dispatched Date Invoiced Cust ID Cust Name Order Item Order No Item No Item Price Num Ordered 9/25/2001 SIMS 257: Database Management Order Item Order No Item No Item Price Num Ordered 9/25/2001 SIMS 257: Database Management Today • Physical Database Design • Access Methods • Indexes Based on McFadden Modern Database Management and Atre Database:Structured Techniques for Design, Performance and Management 9/25/2001 SIMS 257: Database Management Database Design Process Application 1 External Model Application 2 Application 3 Application 4 External Model External Model External Model Application 1 Conceptual requirements Application 2 Conceptual requirements Application 3 Conceptual requirements Conceptual Model Logical Model Internal Model Application 4 Conceptual requirements 9/25/2001 Physical Design SIMS 257: Database Management Physical Database Design • Many physical database design decisions are implicit in the technology adopted – Also, organizations may have standards or an “information architecture” that specifies operating systems, DBMS, and data access languages -- thus constraining the range of possible physical implementations. • We will be concerned with some of the possible physical implementation issues 9/25/2001 SIMS 257: Database Management Physical Database Design • The primary goal of physical database design is data processing efficiency • We will concentrate on choices often available to optimize performance of database services • Physical Database Design requires information gathered during earlier stages of the design process 9/25/2001 SIMS 257: Database Management Physical Design Information • Information needed for physical file and database design includes: – Normalized relations plus size estimates for them – Definitions of each attribute – Descriptions of where and when data are used • entered, retrieved, deleted, updated, and how often – Expectations and requirements for response time, and data security, backup, recovery, retention and integrity – Descriptions of the technologies used to implement the database 9/25/2001 SIMS 257: Database Management Physical Design Decisions • There are several critical decisions that will affect the integrity and performance of the system. – – – – – 9/25/2001 Storage Format Physical record composition Data arrangement Indexes Query optimization and performance tuning SIMS 257: Database Management Storage Format • Choosing the storage format of each field (attribute). The DBMS provides some set of data types that can be used for the physical storage of fields in the database • Data Type (format) is chosen to minimize storage space and maximize data integrity 9/25/2001 SIMS 257: Database Management Objectives of data type selection • • • • Minimize storage space Represent all possible values Improve data integrity Support all data manipulations • The correct data type should, in minimal space, represent every possible value (but eliminated illegal values) for the associated attribute and can support the required data manipulations (e.g. numerical or string operations) 9/25/2001 SIMS 257: Database Management Access Data Types • • • • • • • • • Numeric (1, 2, 4, 8 bytes, fixed or float) Text (255 max) Memo (64000 max) Date/Time (8 bytes) Currency (8 bytes, 15 digits + 4 digits decimal) Autonumber (4 bytes) Yes/No (1 bit) OLE (limited only by disk space) Hyperlinks (up to 64000 chars) 9/25/2001 SIMS 257: Database Management Access Numeric types • Byte – Stores numbers from 0 to 255 (no fractions). 1 byte • Integer – Stores numbers from –32,768 to 32,767 (no fractions) 2 bytes • Long Integer • Single (Default) – Stores numbers from –2,147,483,648 to 2,147,483,647 (no fractions). 4 bytes – Stores numbers from -3.402823E38 to –1.401298E–45 for negative values and from 1.401298E–45 to 3.402823E38 for positive values. 4 bytes • Double – Stores numbers from –1.79769313486231E308 to – 4.94065645841247E–324 for negative values and from 1.79769313486231E308 to 4.94065645841247E–324 for positive values. 15 8 bytes • Replication ID – Globally unique identifier (GUID) 9/25/2001 SIMS 257: Database Management N/A 16 bytes Controlling Data Integrity • • • • • Default values Range control Null value control Referential integrity Handling missing data 9/25/2001 SIMS 257: Database Management Designing Physical Records • A physical record is a group of fields stored in adjacent memory locations and retrieved together as a unit • Fixed Length and variable fields 9/25/2001 SIMS 257: Database Management Designing Physical Files/Internal Model • Overview • terminology • Access methods 9/25/2001 SIMS 257: Database Management Physical Design • Internal Model/Physical Model User request Interface 1 External Model DBMS Internal Model Access Methods Interface 2 Operating System Access Methods Interface 3 Data Base 9/25/2001 SIMS 257: Database Management Physical Design • Interface 1: User request to the DBMS. The user presents a query, the DBMS determines which physical DBs are needed to resolve the query • Interface 2: The DBMS uses an internal model access method to access the data stored in a logical database. • Interface 3: The internal model access methods and OS access methods access the physical records of the database. 9/25/2001 SIMS 257: Database Management Physical File Design • A Physical file is a portion of secondary storage (disk space) allocated for the purpose of storing physical records • Pointers - a field of data that can be used to locate a related field or record of data • Access Methods - An operating system algorithm for storing and locating data in secondary storage • Pages - The amount of data read or written in one disk input or output operation 9/25/2001 SIMS 257: Database Management Internal Model Access Methods • Many types of access methods: – – – – – – Physical Sequential Indexed Sequential Indexed Random Inverted Direct Hashed • Differences in – Access Efficiency – Storage Efficiency 9/25/2001 SIMS 257: Database Management Physical Sequential • Key values of the physical records are in logical sequence • Main use is for “dump” and “restore” • Access method may be used for storage as well as retrieval • Storage Efficiency is near 100% • Access Efficiency is poor (unless fixed size physical records) 9/25/2001 SIMS 257: Database Management Indexed Sequential • Key values of the physical records are in logical sequence • Access method may be used for storage and retrieval • Index of key values is maintained with entries for the highest key values per block(s) • Access Efficiency depends on the levels of index, storage allocated for index, number of database records, and amount of overflow • Storage Efficiency depends on size of index and volatility of database 9/25/2001 SIMS 257: Database Management Index Sequential Data File Actual Value 9/25/2001 Address Block Number Dumpling 1 Harty 2 Texaci 3 ... … Adams Becker Dumpling SIMS 257: Database Management Block 1 Getta Harty Block 2 Mobile Sunoci Texaci Block 3 Indexed Sequential: Two Levels Key Value Key Value 150 1 385 2 001 003 . . 150 Address 385 7 678 8 805 9 … Key Value 251 . . 385 Address 536 3 678 4 Key Value 9/25/2001 Address 455 480 . . 536 605 610 . . 678 Address 785 5 805 6 SIMS 257: Database Management 791 . . 805 705 710 . . 785 Indexed Random • Key values of the physical records are not necessarily in logical sequence • Index may be stored and accessed with Indexed Sequential Access Method • Index has an entry for every data base record. These are in ascending order. The index keys are in logical sequence. Database records are not necessarily in ascending sequence. • Access method may be used for storage and retrieval 9/25/2001 SIMS 257: Database Management Indexed Random Becker Harty Actual Value Address Block Number Adams 2 Becker 1 Dumpling 3 Getta 2 Harty 1 Adams Getta Dumpling 9/25/2001 SIMS 257: Database Management Btree F B || D || F| || P || Z| H || L || P| R || S || Z| Devils Aces Boilers Cars 9/25/2001 Flyers Hawkeyes Hoosiers Minors Panthers SIMS 257: Database Management Seminoles Inverted • Key values of the physical records are not necessarily in logical sequence • Access Method is better used for retrieval • An index for every field to be inverted may be built • Access efficiency depends on number of database records, levels of index, and storage allocated for index 9/25/2001 SIMS 257: Database Management Inverted CH 145 101, 103,104 Actual Value Address Block Number CH 145 1 CS 201 2 CS 623 3 PH 345 … CS 201 102 CS 623 105, 106 9/25/2001 SIMS 257: Database Management Student name Course Number Adams CH145 Becker cs201 Dumpling ch145 Getta ch145 Harty cs623 Mobile cs623 Direct • Key values of the physical records are not necessarily in logical sequence • There is a one-to-one correspondence between a record key and the physical address of the record • May be used for storage and retrieval • Access efficiency always 1 • Storage efficiency depends on density of keys • No duplicate keys permitted 9/25/2001 SIMS 257: Database Management Hashing • Key values of the physical records are not necessarily in logical sequence • Many key values may share the same physical address (block) • May be used for storage and retrieval • Access efficiency depends on distribution of keys, algorithm for key transformation and space allocated • Storage efficiency depends on distibution of keys and algorithm used for key transformation 9/25/2001 SIMS 257: Database Management Comparative Access Methods Factor Storage space Sequential retrieval on primary key Random Retr. Multiple Key Retr. Deleting records Sequential No wasted space Indexed Hashed No wasted space for data but extra space for index more space needed for addition and deletion of records after initial load Very fast Moderately Fast Impractical Moderately Fast Impractical Possible but needs Very fast with multiple indexes a full scan can create wasted OK if dynamic space OK if dynamic Adding records requires rewriting file Easy but requires Maintenance of Updating records usually requires indexes rewriting file 9/25/2001 SIMS 257: Database Management Very fast Not possible very easy very easy very easy