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Referential Integrity and Database Design Recap: From Conceptual Design to Physical Relational Implementation University of California, Berkeley School of Information IS 257: Database Management IS 257 – Fall 2009 2009-09-22 SLIDE 1 Lecture Outline • Review – Physical Database Design – Access Methods – Indexes and What to index – Parallel storage systems (RAID) • Integrity constraints • Database Design Process Recap IS 257 – Fall 2009 2009-09-22 SLIDE 2 Lecture Outline • Review – Physical Database Design – Access Methods – Indexes and What to index – Parallel storage systems (RAID) • Integrity constraints • Database Design Process Recap IS 257 – Fall 2009 2009-09-22 SLIDE 3 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 IS 257 – Fall 2009 Physical Design 2009-09-22 SLIDE 4 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 IS 257 – Fall 2009 2009-09-22 SLIDE 5 Physical Design Decisions • There are several critical decisions that will affect the integrity and performance of the system. – Storage Format – Physical record composition – Data arrangement – Indexes – Query optimization and performance tuning IS 257 – Fall 2009 2009-09-22 SLIDE 6 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) IS 257 – Fall 2009 2009-09-22 SLIDE 7 Lecture Outline • Review – Physical Database Design – Access Methods – Indexes and What to index – Parallel storage systems (RAID) • Integrity constraints • Database Design Process Recap IS 257 – Fall 2009 2009-09-22 SLIDE 8 Internal Model Access Methods • Many types of access methods: – Physical Sequential – Indexed Sequential – Indexed Random – Inverted – Direct – Hashed • Differences in – Access Efficiency – Storage Efficiency IS 257 – Fall 2009 2009-09-22 SLIDE 9 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) IS 257 – Fall 2009 2009-09-22 SLIDE 10 Index Sequential Data File Actual Value IS 257 – Fall 2009 Address Block Number Dumpling 1 Harty 2 Texaci 3 ... … Adams Becker Dumpling Block 1 Getta Harty Block 2 Mobile Sunoci Texaci Block 3 2009-09-22 SLIDE 11 Indexed Sequential: Two Levels Key Value Key Value Address 150 1 385 2 001 003 . . 150 Address 385 7 678 8 805 9 … Key Value Address 536 3 678 4 Key Value 251 . . 385 455 480 . . 536 605 610 . . 678 Address 785 5 805 6 791 . . 805 IS 257 – Fall 2009 705 710 . . 785 2009-09-22 SLIDE 12 Indexed Random Becker Harty Actual Value Address Block Number Adams 2 Becker 1 Dumpling 3 Getta 2 Harty 1 Adams Getta Dumpling IS 257 – Fall 2009 2009-09-22 SLIDE 13 Btree F B || D || F| || P || Z| H || L || P| R || S || Z| Devils Aces Boilers Cars IS 257 – Fall 2009 Flyers Hawkeyes Hoosiers Minors Panthers Seminoles 2009-09-22 SLIDE 14 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 Student name Course Number Adams CH145 Becker cs201 Dumpling ch145 Getta ch145 Harty cs623 Mobile cs623 CS 623 105, 106 IS 257 – Fall 2009 2009-09-22 SLIDE 15 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 IS 257 – Fall 2009 2009-09-22 SLIDE 16 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 IS 257 – Fall 2009 2009-09-22 SLIDE 17 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 Very fast with multiple indexes OK if dynamic Very fast OK if dynamic very easy Easy but requires Maintenance of indexes very easy Impractical Possible but needs a full scan can create wasted space Adding records requires rewriting file Updating records usually requires rewriting file IS 257 – Fall 2009 Not possible very easy 2009-09-22 SLIDE 18 Late addition – Bitmap index • Uses a single bit to represent whether or not a particular record has a specific value IS 257 – Fall 2009 2009-09-22 SLIDE 19 Lecture Outline • Review – Physical Database Design – Access Methods – Indexes and What to index – Parallel storage systems (RAID) • Integrity constraints • Database Design Process Recap IS 257 – Fall 2009 2009-09-22 SLIDE 20 Indexes • Most database applications require: – locating rows in tables that match some condition (e.g. SELECT operations) – Joining one table with another based on common values of attributes in each table • Indexes can greatly speed up these processes and avoid having to do sequential scanning of database tables to resolve queries IS 257 – Fall 2009 2009-09-22 SLIDE 21 Primary Key Indexes • In Access -- this will be created automatically when a field is selected as primary key – in the table design view select an attribute row (or rows) and clock on the key symbol in the toolbar. – The index is created automatically as one with (No Duplicates) • In SQL – CREATE UNIQUE INDEX indexname ON tablename(attribute); IS 257 – Fall 2009 2009-09-22 SLIDE 22 Secondary Key Indexes • In Access -- Secondary key indexes can be created on any field. – In the table design view, select the attribute to be indexed – In the “Indexed” box on the General field description information at the bottom of the window, select “Yes (Duplicates OK)” • In SQL – CREATE INDEX indxname on tablename(attribute); IS 257 – Fall 2009 2009-09-22 SLIDE 23 When to Index • Tradeoff between time and space: – Indexes permit faster processing for searching – But they take up space for the index – They also slow processing for insertions, deletions, and updates, because both the table and the index must be modified • Thus they SHOULD be used for databases where search is the main mode of interaction • The might be skipped if high rates of updating and insertions are expected, and access or operations are rare IS 257 – Fall 2009 2009-09-22 SLIDE 24 When to Use Indexes • Rules of thumb – Indexes are most useful on larger tables – Specify a unique index for the primary key of each table (automatically done for many DBMS) – Indexes are most useful for attributes used as search criteria or for joining tables – Indexes are useful if sorting is often done on the attribute – Most useful when there are many different values for an attribute – Some DBMS limit the number of indexes and the size of the index key values – Some indexes will not retrieve NULL values IS 257 – Fall 2009 2009-09-22 SLIDE 25 Lecture Outline • Review – Physical Database Design – Access Methods – Indexes and What to index – Parallel storage systems (RAID) • Integrity constraints • Database Design Process Recap IS 257 – Fall 2009 2009-09-22 SLIDE 26 Parallel Processing with RAID • In reading pages from secondary storage, there are often situations where the DBMS must retrieve multiple pages of data from storage -- and may often encounter – rotational delay – seek positioning delay • in getting each page from the disk IS 257 – Fall 2009 2009-09-22 SLIDE 27 Disk Timing (and Problems) Rotational Delay Seek Positioning Delay Hair Read Head fingerprint IS 257 – Fall 2009 2009-09-22 SLIDE 28 RAID • Provides parallel disks (and software) so that multiple pages can be retrieved simultaneously • RAID stands for “Redundant Arrays of Inexpensive Disks” – invented by Randy Katz and Dave Patterson here at Berkeley • Some manufacturers have renamed the “inexpensive” part (for obvious reasons) IS 257 – Fall 2009 2009-09-22 SLIDE 29 RAID Technology One logical disk drive Parallel Writes Disk 1 Disk 2 Disk 3 Disk 4 1 5 2 6 3 7 4 8 9 * * * 10 * * * 11 * * * 12 * * * Stripe Stripe Stripe Parallel Reads IS 257 – Fall 2009 2009-09-22 SLIDE 30 Raid 0 One logical disk drive Parallel Writes Disk 1 Disk 2 Disk 3 Disk 4 1 5 2 6 3 7 4 8 9 * * * 10 * * * 11 * * * 12 * * * Stripe Stripe Stripe Parallel Reads IS 257 – Fall 2009 2009-09-22 SLIDE 31 RAID-1 Parallel Writes Disk 1 Disk 2 Disk 3 Disk 4 1 3 1 3 2 4 2 4 5 * * * 5 * * * 6 * * * 6 * * * Stripe Stripe Stripe Parallel Reads Raid 1 provides full redundancy for any data stored IS 257 – Fall 2009 2009-09-22 SLIDE 32 RAID-2 Writes span all drives Disk 1 Disk 2 Disk 3 Disk 4 1a 2a 1b 2b ecc ecc ecc ecc 3a * * * 3b * * * ecc ecc * * * * * * Stripe Stripe Stripe Reads span all drives Raid 2 divides blocks across multiple disks with error correcting codes IS 257 – Fall 2009 2009-09-22 SLIDE 33 RAID-3 Writes span all drives Disk 1 Disk 2 Disk 3 Disk 4 1a 2a 1b 2b 1c 2c ecc ecc 3a * * * 3b * * * 3c * * * ecc * * * Stripe Stripe Stripe Reads span all drives Raid 3 divides very long blocks across multiple disks with a single drive for ECC IS 257 – Fall 2009 2009-09-22 SLIDE 34 Raid-4 Parallel Writes Disk 1 Disk 2 Disk 3 Disk 4 1 4 2 5 3 6 ecc ecc 7 * * * 8 * * * 9 * * * ecc * * * Stripe Stripe Stripe Parallel Reads Raid 4 like Raid 3 for smaller blocks with multiple blocks per stripe IS 257 – Fall 2009 2009-09-22 SLIDE 35 RAID-5 Parallel Writes Disk 1 Disk 2 1 5 9 * * ecc 2 6 10 * * ecc Disk 3 3 7 11 * * ecc Disk 4 4 8 12 * * ecc Stripe Stripe Stripe Parallel Reads Raid 5 divides blocks across multiple disks with error correcting codes IS 257 – Fall 2009 2009-09-22 SLIDE 36 RAID for DBMS • What works best for Database storage? • RAID-1 is best when 24/7 fault tolerant processing is needed • RAID-5 is best for read-intensive applications with very large data sets IS 257 – Fall 2009 2009-09-22 SLIDE 37 Lecture Outline • Review – Physical Database Design – Access Methods – Indexes and What to index – Parallel storage systems (RAID) • Integrity constraints • Database Design Process Recap IS 257 – Fall 2009 2009-09-22 SLIDE 38 Integrity Constraints • The constraints we wish to impose in order to protect the database from becoming inconsistent. • Five types – Required data – attribute domain constraints – entity integrity – referential integrity – enterprise constraints IS 257 – Fall 2009 2009-09-22 SLIDE 39 Required Data • Some attributes must always contain a value -- they cannot have a null • For example: – Every employee must have a job title. – Every diveshop diveitem must have an order number and an item number. IS 257 – Fall 2009 2009-09-22 SLIDE 40 Attribute Domain Constraints • Every attribute has a domain, that is a set of values that are legal for it to use. • For example: – The domain of sex in the employee relation is “M” or “F” • Domain ranges can be used to validate input to the database. IS 257 – Fall 2009 2009-09-22 SLIDE 41 Entity Integrity • The primary key of any entity cannot be NULL. IS 257 – Fall 2009 2009-09-22 SLIDE 42 Referential Integrity • A “foreign key” links each occurrence in a relation representing a child entity to the occurrence of the parent entity containing the matching candidate key • Referential Integrity means that if the foreign key contains a value, that value must refer to an existing occurrence in the parent entity • For example: – Since the Order ID in the diveitem relation refers to a particular diveords item, that item must exist for referential integrity to be satisfied IS 257 – Fall 2009 2009-09-22 SLIDE 43 Referential Integrity • Referential integrity options are declared when tables are defined (in most systems) • There are many issues having to do with how particular referential integrity constraints are to be implemented to deal with insertions and deletions of data from the parent and child tables. IS 257 – Fall 2009 2009-09-22 SLIDE 44 Insertion rules • A row should not be inserted in the referencing (child) table unless there already exists a matching entry in the referenced table. • Inserting into the parent table should not cause referential integrity problems – Unless it is itself a child… • Sometimes a special NULL value may be used to create child entries without a parent or with a “dummy” parent. IS 257 – Fall 2009 2009-09-22 SLIDE 45 Deletion rules • A row should not be deleted from the referenced table (parent) if there are matching rows in the referencing table (child). • Three ways to handle this – Restrict -- disallow the delete – Nullify -- reset the foreign keys in the child to some NULL or dummy value – Cascade -- Delete all rows in the child where there is a foreign key matching the key in the parent row being deleted IS 257 – Fall 2009 2009-09-22 SLIDE 46 Referential Integrity • This can be implemented using external programs that access the database • newer databases implement executable rules or built-in integrity constraints (e.g. Access) IS 257 – Fall 2009 2009-09-22 SLIDE 47 Enterprise Constraints • These are business rule that may affect the database and the data in it – for example, if a manager is only permitted to manage 10 employees then it would violate an enterprise constraint to manage more IS 257 – Fall 2009 2009-09-22 SLIDE 48 Outline • Review – Physical Database Design – Access Methods – Indexes and What to index – Parallel storage systems (RAID) • Integrity constraints • Database Design Process Recap IS 257 – Fall 2009 2009-09-22 SLIDE 49 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 IS 257 – Fall 2009 2009-09-22 SLIDE 50 Today: New Design • Today we will build the COOKIE database from (rough) needs assessment through the conceptual model, logical model and finally physical implementation in Access. IS 257 – Fall 2009 2009-09-22 SLIDE 51 Cookie Requirements • Cookie is a bibliographic database that contains information about a hypothetical union catalog of several libraries. • Need to record which books are held by which libraries • Need to search on bibliographic information – Author, title, subject, call number for a given library, etc. • Need to know who publishes the books for ordering, etc. IS 257 – Fall 2009 2009-09-22 SLIDE 52 Cookie Database • There are currently 6 main types of entities in the database – Authors (Authors) • Note: we created authors from the former design when talking about normalization (two weeks ago) – – – – – – Books (bibfile) Local Call numbers (callfile) Libraries (libfile) Publishers (pubfile) Subject headings (subfile) Additional entities • Links between subject and books (indxfile) • Links between authors and books (AU_BIB) IS 257 – Fall 2009 2009-09-22 SLIDE 53 AUTHORS • Author -- The author’s name (We do not distinguish between Personal and Corporate authors) • Au_id – a unique id for the author IS 257 – Fall 2009 2009-09-22 SLIDE 54 AUTHORS AU ID Author Authors IS 257 – Fall 2009 2009-09-22 SLIDE 55 BIBFILE • Books (BIBFILE) contains information about particular books. It includes one record for each book. The attributes are: – – – – – – – – accno -- an “accession” or serial number title -- The title of the book loc -- Location of publication (where published) date -- Date of publication price -- Price of the book pagination -- Number of pages ill -- What type of illustrations (maps, etc) if any height -- Height of the book in centimeters IS 257 – Fall 2009 2009-09-22 SLIDE 56 Books/BIBFILE Title accno Loc Price Books Date Pagination Ill Height IS 257 – Fall 2009 2009-09-22 SLIDE 57 CALLFILE • CALLFILE contains call numbers and holdings information linking particular books with particular libraries. Its attributes are: – accno -- the book accession number – libid -- the id of the holding library – callno -- the call number of the book in the particular library – copies -- the number of copies held by the particular library IS 257 – Fall 2009 2009-09-22 SLIDE 58 LocalInfo/CALLFILE libid Callno accno Copies CALLFILE IS 257 – Fall 2009 2009-09-22 SLIDE 59 LIBFILE • LIBFILE contain information about the libraries participating in this union catalog. Its attributes include: – – – – – – – – libid -- Library id number library -- Name of the library laddress -- Street address for the library lcity -- City name lstate -- State code (postal abbreviation) lzip -- zip code lphone -- Phone number mop - suncl -- Library opening and closing times for each day of the week. IS 257 – Fall 2009 2009-09-22 SLIDE 60 Libraries/LIBFILE lstate laddress lcity lzip Library lphone Libid SatCl LIBFILE SunOp SatOp Suncl FCl MOp FOp ThCl Mcl TuOp IS 257 – Fall 2009 TuCl WOp WCl ThOp 2009-09-22 SLIDE 61 PUBFILE • PUBFILE contain information about the publishers of books. Its attributes include – pubid -- The publisher’s id number – publisher -- Publisher name – paddress -- Publisher street address – pcity -- Publisher city – pstate -- Publisher state – pzip -- Publisher zip code – pphone -- Publisher phone number – ship -- standard shipping time in days IS 257 – Fall 2009 2009-09-22 SLIDE 62 Publisher/PUBFILE paddress Publisher pcity PUBFILE pubid pstate pzip Ship pphone IS 257 – Fall 2009 2009-09-22 SLIDE 63 SUBFILE • SUBFILE contains each unique subject heading that can be assigned to books. Its attributes are – subcode -- Subject identification number – subject -- the subject heading/description IS 257 – Fall 2009 2009-09-22 SLIDE 64 Subjects/SUBFILE subid Subject SUBFILE IS 257 – Fall 2009 2009-09-22 SLIDE 65 INDXFILE • INDXFILE provides a way to allow manyto-many mapping of subject headings to books. Its attributes consist entirely of links to other tables – subcode -- link to subject id – accno -- link to book accession number IS 257 – Fall 2009 2009-09-22 SLIDE 66 Linking Subjects and Books subid ACCNO INDXFILE IS 257 – Fall 2009 2009-09-22 SLIDE 67 AU_BIB • AU_BIB provides a way to allow many to many mapping between books and authors. It also consists only of links to other tables – AU_ID – link to the AUTHORS table – ACCNO – link to the BIBFILE table IS 257 – Fall 2009 2009-09-22 SLIDE 68 Linking Authors and Books AU ID ACCNO AU_BIB IS 257 – Fall 2009 2009-09-22 SLIDE 69 Some examples of Cookie Searches • Who wrote Microcosmographia Academica? • How many pages long is Alfred Whitehead’s The Aims of Education and Other Essays? • Which branches in Berkeley’s public library system are open on Sunday? • What is the call number of Moffitt Library’s copy of Abraham Flexner’s book Universities: American, English, German? • What books on the subject of higher education are among the holdings of Berkeley (both UC and City) libraries? • Print a list of the Mechanics Library holdings, in descending order by height. • What would it cost to replace every copy of each book that contains illustrations (including graphs, maps, portraits, etc.)? • Which library closes earliest on Friday night? IS 257 – Fall 2009 2009-09-22 SLIDE 70 Cookie ER Diagram pubid accno BIBFILE CALLFILE accno accno AU_BIB LIBFILE libid libid AU ID PUBFILE INDXFILE pubid SUBFILE AUTHORS accno AU_ID subcode subcode Note: diagram contains only attributes used for linking Author IS 257 – Fall 2009 2009-09-22 SLIDE 71 What Problems? • What sorts of problems and missing features arise given the previous ER diagram? IS 257 – Fall 2009 2009-09-22 SLIDE 72 Problems Identified • • • • • • • • Subtitles, parallel titles? Edition information Series information lending status material type designation Genre, class information Better codes (ISBN?) Missing information (ISBN) IS 257 – Fall 2009 • Authority control for authors • Missing/incomplete data • Data entry problems • Ordering information • Illustrations • Subfield separation (such as last_name, first_name) • Separate personal and corporate authors 2009-09-22 SLIDE 73 Problems (Cont.) • Location field inconsistent • No notes field • No language field • Zipcode doesn’t support plus-4 • No publisher shipping addresses IS 257 – Fall 2009 • No (indexable) keyword search capability • No support for multivolume works • No support for URLs – to online version – to libraries – to publishers 2009-09-22 SLIDE 74 Original Cookie ER Diagram pubid accno BIBFILE CALLFILE accno accno AU_BIB LIBFILE libid libid AU ID PUBFILE INDXFILE pubid SUBFILE AUTHORS accno AU_ID subcode subcode Note: diagram contains only attributes used for linking Author IS 257 – Fall 2009 2009-09-22 SLIDE 75 Cookie2: Separate Name Authorities pubid accno BIBFILE CALLFILE accno accno AUTHBIB LIBFILE libid libid authid PUBFILE authtype INDXFILE pubid SUBFILE AUTHFILE accno authid subcode subcode name nameid IS 257 – Fall 2009 2009-09-22 SLIDE 76 Cookie 3: Keywords termid accno termid pubid accno BIBFILE accno AUTHBIB KEYMAP TERMS CALLFILE LIBFILE accno libid authid libid PUBFILE authtype INDXFILE pubid SUBFILE AUTHFILE authid name accno subcode subcode nameid IS 257 – Fall 2009 2009-09-22 SLIDE 77 Cookie 4: Series ser_title SERIES seriesid termid accno termid seriesid pubid accno BIBFILE accno AUTHBIB KEYMAP TERMS CALLFILE LIBFILE accno libid authid libid PUBFILE authtype INDXFILE pubid SUBFILE AUTHFILE authid name accno subcode subcode nameid IS 257 – Fall 2009 2009-09-22 SLIDE 78 Cookie 5: Circulation ser_title SERIES seriesid pubid KEYMAP TERMS CALLFILE LIBFILE accno BIBFILE accno termid accno termid seriesid accno circid libid libid AUTHBIB authid PUBFILE pubid authtype AUTHFILE authid nameid name IS 257 – Fall 2009 INDXFILE SUBFILE accno subcode subcode PATRON CIRC copynum patronid circid 2009-09-22 SLIDE 79 Logical Model: Mapping to Relations • Take each entity – Authors – BIBFILE – LIBFILE – CALLFILE – SUBFILE – PUBFILE – INDXFILE – AU_BIB • And make it a table... IS 257 – Fall 2009 2009-09-22 SLIDE 80 Implementing the Physical Database... • For each of the entities, we will build a table… • Start up access… • Use “New” in Tables… • Loading data • Entering data • Data entry forms IS 257 – Fall 2009 2009-09-22 SLIDE 81 Database Creation in Access • Simplest to use a design view – wizards are available, but less flexible • Need to watch the default values • Helps to know what the primary key is, or if one is to be created automatically – Automatic creation is more complex in other RDBMS and ORDBMS • Need to make decision about the physical storage of the data IS 257 – Fall 2009 2009-09-22 SLIDE 82 Next Time • • • • Relational Operations Relational Algebra Relational Calculus Introduction to SQL IS 257 – Fall 2009 2009-09-22 SLIDE 83