implementing entity relationship models relational databases

... Khóa ngoại 36 Chương Thực thể sang bảng: 4.Weak -entity Emp_ID Dept_DOB Emp_Name Dept_Name EMPLOYEE Dept_Gender DEPENDENT “Strong entity “Weak entity EMPLOYEE Emp_ID Employee_Name DEPENDENT ... liệu 30 Chuyển đổi từ ERD sang bảng quan hệ (table) quan hệ bảng (relationship) , để phù hợp với hệ quản trị CSDL phổ biến loại Relational Database(RD) Thiết lập chế ràng buộc toàn vẹn liệu để ... đệ quy 15 Chương ISA Entity (thực thể cha-con) 16  Cho hai tập thực thể A B Ta nói A có mối quan hệ ISA với B thực thể A thực thể B (còn gọi A B)  Ký hiệu Chương ISA Entity (thực thể cha-con)...

Ngày tải lên: 14/03/2013, 16:45

... Đầu Chức xóa khách hàng a Mục đích b Đầu vào c Các trình thực d Đầu PHẦN IV: System Designs Entity Relationship Diagram I Các kiểu thực thể Thực thể (TT) Khách hàng Mã KH Mật Họ Tên Ngàyđăng...

Ngày tải lên: 28/04/2013, 17:23

... riêng Không thể giản đồ ER Entity, Entity Type, Entity Set  Loại thực thể (entity type)   Một tập hợp thực thể có thuộc tính có giá trị khác thuộc tính Tập thực thể (entity set)  Một tập hợp ... quan hệ từ giản đồ ER Các ký hiệu mô hình ER … Entity Type Composite Attribute Weak Entity Type Derived Attribute Relationship Type Identifying Relationship Type E1 E2 R Total Participation of ... hợp    Mối kết hợp (relationship) : liên hệ với hai hay nhiều thực thể khác mang ý nghĩa Tập mối kết hợp (relationship set): mối kết hợp có loại kết hợp Loại mối kết hợp (relationship type): thực...

Ngày tải lên: 19/09/2013, 00:31

... subject of relational databases Most databases in use today are relational, and the focus in this book will be to design a relational database Before we can actually get into relational databases, ... the entity, attributes, relationships, and the "one -entity" ER diagram Steps 1, 2, and of the ER Design Methodology are developed The "one -entity" grammar and mapping rules for the" one -entity" ... Database — Some Definitions: Entity, Relationship, Attribute As the name implies, an ER diagram models data as entities and relationships, and entities have attributes An entity is a thing about which...

Ngày tải lên: 22/10/2013, 10:15

... needed to write web interfaces to their databases, or add databases to drive their web interfaces Whichever way you look at it, they needed to connect to the databases in order to use them CGI is ... provides the flexibility of DBD::mysql in this regard Running Two or More Relational Databases Sometimes you end up running many databases on the same machine These might have very different needs ... instead of having a maximum of 40 open connections, you may end up with 80 574 | Chapter 20: Relational Databases and mod_perl This is the Title of the Book, eMatter Edition Copyright © 2004 O’Reilly...

Ngày tải lên: 24/10/2013, 08:15

... MANAGING TIME IN RELATIONAL DATABASES Companion Web site Ancillary materials are available online at: www.elsevierdirect.com/companions/9780123750419 MANAGING TIME IN RELATIONAL DATABASES How to ... implemented in non -relational databases also For that matter, they can be implemented with a set of flat files We use the language of relational technology simply because the ubiquity of relational database ... One objective of this book is to describe how to manage uni-temporal and bi-temporal data in relational databases in such a way that they can be seamlessly accessed together with current data.1...

Ngày tải lên: 24/12/2013, 02:16

... over the last two decades Nor is it how they think of warehouses and marts Managing Time in Relational Databases Doi: 10.1016/B978-0-12-375041-9.00023-6 Copyright # 2010 Elsevier Inc All rights ... book, we use the terminology of relational technology, a terminology understood by data management professionals, rather than the less wellunderstood terminology of relational theory Thus, we talk ... HISTORY OF TEMPORAL DATA MANAGEMENT CONTENTS Excluding Time from Databases: A Ubiquitous Paradigm 12 The 1980s 13 Historical Databases 13 History Tables 13 The 1990s 14 Temporal Extensions to...

Ngày tải lên: 24/12/2013, 02:16

... have the relational model, a model invented by Dr E F Codd An underlying assumption of the relational model is that it deals with current data only But temporal data can be managed with relational ... which is a set of non-looping (acyclic) one-to-many relationships In each relationship, the item on the “one” side is called the parent item in the relationship, and the one or more items on the “many” ... in data models for many years They are the exclusive subtype hierarchies defined in logical data models, and in the (single-inheritance) class hierarchies defined in object-oriented models An...

Ngày tải lên: 24/12/2013, 02:16

... applicability to real-world problems So “the relational model”, as we use the term, for example, means something like relational theory as implemented in current relational technology” Chapter A TAXONOMY ... uni-temporal models The Alternative Temporal Model What we call the alternative temporal model was developed by Chris Date, Hugh Darwen and Dr Nikos Lorentzos in their book Temporal Data and the Relational ... non-temporal table, each row must conform to entity integrity and referential integrity constraints In an asserted version table, each version must conform to temporal entity integrity and temporal referential...

Ngày tải lên: 24/12/2013, 02:16

... to manage pipeline datasets as distinct physical objects Allen Relationships Allen relationships describe all possible positional relationships between two time periods along a common timeline ... clock tick in length There are 13 Allen relationships in total Six have a corresponding inverse relationship, and one does not Standard treatments of the Allen relationships may be found in both [2000, ... inverse Thus, this taxonomy specifies 13 leafnode relationships which are, in fact, precisely the 13 Allen relationships The names of the Allen relationships are standard, and have been since Allen...

Ngày tải lên: 24/12/2013, 02:16

... the temporal analogs of entity integrity and referential integrity Temporal entity integrity is entity integrity applied to temporal tables But we need to understand what entity integrity applied ... properties and relationships, both of which appear in databases as columns of tables Each row represents an object, and each column instance represents either a property of an object, or a relationship ... event In the case of a many-to-many relationship in which an object is involved, each instance of the relationship is a row in a separate table, one that relational theory calls an associative...

Ngày tải lên: 24/12/2013, 02:16

... Integrity Constraints The three integrity constraints in relational theory are entity integrity, referential integrity and domain integrity Entity integrity insures that the object represented by ... Temporal Entity Integrity Breaking the one-to-one correspondence between objects and rows is no small thing Its implications are significant One of them is that the relational rule of entity integrity ... both entity integrity and temporal entity integrity play the same semantic role; they both prevent conflicting truth claims However, TEI has additional work to do, work that is not required of entity...

Ngày tải lên: 24/12/2013, 02:16

... our method of temporal data management in great detail, we will sometimes Managing Time in Relational Databases Doi: 10.1016/B978-0-12-375041-9.00007-8 Copyright # 2010 Elsevier Inc All rights ... object could be indistinguishable We also point out that without the AVF code to enforce temporal entity integrity, these two dates could not prevent overlapping versions For example, P[P861[Mar10-Nov10]] ... and in this case, there is a 6month overlap of these two time periods The AVF enforces temporal entity integrity on the basis of an interpretation of these date pairs as time period delimiters...

Ngày tải lên: 24/12/2013, 02:16

Ngày tải lên: 21/01/2014, 05:20

... episodes In the non-temporal case, this constraint is known as entity integrity In the Asserted Versioning case, it is what we call temporal entity integrity (TEI) The physical transaction is derived ... Update: Before the First Physical Transaction is a temporal foreign key (TFK), implementing a temporal referential integrity relationship (TRI) It designates an object in a referenced asserted version ... DESIGNING, MAINTAINING AND QUERYING ASSERTED VERSION DATABASES Chapter Contents 10 11 12 13 14 15 16 Designing and Generating Asserted Versioning Databases An Introduction to Temporal Transactions...

Ngày tải lên: 21/01/2014, 08:20

... VERSIONING DATABASES enrolled in any number of wellness programs, each of which may enroll any number of clients Thus, the entity Wellness Program Enrollment is an associative entity, implementing ... done without making any changes to the logical data models of those databases Temporality is introduced “downstream” from the logical data models, by making entries in asserted version metadata ... that logical data models of conventional databases, developed perhaps years ago, not have to be changed if a decision is made to convert one or more of the tables in those databases into bi-temporal...

Ngày tải lên: 21/01/2014, 08:20

... the model itself In fact, the logical data models of Asserted Versioning databases are indistinguishable from the logical data models of conventional databases Apparent Redundancies in the Asserted ... VERSIONING DATABASES the semantic constraints without which those tables would just be a collection of columns with nothing particularly temporal about them at all Generating Temporal Entity and ... not that row has an Allen relationship with the assertion time specified on a query To determine that, we 187 188 Chapter DESIGNING AND GENERATING ASSERTED VERSIONING DATABASES would need to know...

Ngày tải lên: 21/01/2014, 08:20

... an entity integrity or a referential integrity constraint, it will reject that transaction In response, the AVF will stop processing the temporal transaction, undo Managing Time in Relational Databases ... that matters to the AVF It is a matter of the relationship between when the transaction takes place, and what period of effective time it affects As a relationship between a point in time and a ... the Transaction In Allen relationship terms, one cannot be [before] the other However, since one clearly is before the other, as we understand the word “before”, Allen relationship terminology...

Ngày tải lên: 21/01/2014, 08:20

... integrity (RI), at the level of types rather than instances, is a relationship between two relational Managing Time in Relational Databases Doi: 10.1016/B978-0-12-375041-9.00011-X Copyright # 2010 ... database An Allen Relationship Completeness Check First of all, it is well established that the Allen relationships are a mutually exclusive and jointly exhaustive set of all the possible relationships ... [beforeÀ1], [meets] and [meetsÀ1] relationships are subtypes, in our taxonomy, of the [excludes] relationship And we can now see why this is an important group of relationships to define Temporal...

Ngày tải lên: 21/01/2014, 08:20

... 2010, two months after P861-A did If episodes were the child managed objects in TRI relationships, then this relationship would be invalid But they are not C882-A is the parent to P861-A(1) C903-A ... difference between (i) foreign keys (FKs), the relationships they implement and the constraints they impose, and (ii) temporal foreign keys (TFKs), the relationships they implement and the constraints ... referential integrity relationship, a parent row cannot be deleted as long as any child row exists with a foreign key pointing to it So with a temporal referential integrity relationship, a parent...

Ngày tải lên: 21/01/2014, 08:20