Towards understanding the schema in relational databases

... Consider the columns in the UNIVERSITY database in Figure 1.2 as an example There are six columns in the figure containing integers ranging in different intervals While STUDENT.id fully contains the other ... described in the form of relational schema While the schema provides us a way to specify various properties of the data contained in the databases, inclu...

Ngày tải lên: 10/09/2015, 09:24

... Lgt4 Results In order to investigate the function of the glycosyltransferase enzymes involved in the biosynthesis of LOS of M catarrhalis, and to gain some insights into the mechanism of serotype ... irradiating each of the anomeric signals in turn to obtain the H chemicals shifts of the corresponding remaining ring protons Again, assignment of the Kdo...

Ngày tải lên: 30/03/2014, 08:20

... data in which none of that is necessary, a world in which all pipeline datasets are contained in the single table that is their destination or their point of origin In this world, maintaining ... MANAGING TIME IN RELATIONAL DATABASES Companion Web site Ancillary materials are available online at: www.elsevierdirect.com/companions/9780123750419 MANAGING TIME IN RELATIONA...

Ngày tải lên: 24/12/2013, 02:16

... interested in, two of those components being time periods that may or may not intersect in various ways Continuing on, consider the possibilities involved in joining bi-temporal tables to one another, ... management losing faith in data warehouse projects As these large projects fell increasingly behind schedule and rose increasingly over budget— something large projects tend to do—t...

Ngày tải lên: 24/12/2013, 02:16

... to the point in time we are interested in But the defining feature of reconstructable methods is not the movement of data from off-line to on-line storage The defining feature is the inability ... difference in emphasis which may vary depending on context Managing Time in Relational Databases Doi: 10.1016/B978-0-12-375041-9.00002-9 Copyright # 2010 Elsevier Inc All rights of r...

Ngày tải lên: 24/12/2013, 02:16

... lacking a standard for the PERIOD datatype, we will continue the practice of defining periods of time in terms of their begin and end points in time 59 60 Chapter THE ORIGINS OF ASSERTED VERSIONING: ... record of when business events happen in the real world In addition, for most business purposes, we assume that a SQL timestamp plus a defined interval of time will result in a...

Ngày tải lên: 24/12/2013, 02:16

... point in time may either [intersect] or [exclude] the time period If the point in time [intersects] the time period, it also [fills] and [occupies] that time period If it [aligns] with the time ... ask whether a point in time is or is not contained in a period of time Where P and T are, respectively, a point in time and a period of time, and T1 and T2 are dates de...

Ngày tải lên: 24/12/2013, 02:16

... have been using is inadequate, because it only allows us to pick out a “when in effect” point in time We also need to pick out a “when in the life of the data in the table” point in time And for ... same point in time All effective time relationships exist within shared assertion time Because this is so important to keep in mind, we will often add the qualifier “within...

Ngày tải lên: 24/12/2013, 02:16

... effective time than assertion time, we also present an in- line notation for single asserted Managing Time in Relational Databases Doi: 10.1016/B978-0-12-375041-9.00006-6 Copyright # 2010 Elsevier Inc ... assertion time or effective time on their insert, update or delete transactions, it will seem to them that they are maintaining data in a conventional table This maintenanc...

Ngày tải lên: 24/12/2013, 02:16

... assertion time and effective time is that two or more effective -time [intersecting] versions of the same object, in shared assertion time, would violate temporal entity integrity, making conflicting ... representation of a timeline and a snapshot of effective time periods, grouped by common assertion times along that timeline With the in- line notation, that context, too, is not r...

Ngày tải lên: 24/12/2013, 02:16

... against non-temporal tables insert, update or delete individual rows representing objects, transactions against asserted version tables insert into a period of time, update within a period of time, ... Transaction An insert into a non-temporal table is valid just in case a row for the object does not exist in the target table at the time of the insert In the same way, a temporal ins...

Ngày tải lên: 21/01/2014, 08:20

... tables in those databases into bi-temporal asserted Managing Time in Relational Databases Doi: 10.1016/B978-0-12-375041-9.00008-X Copyright # 2010 Elsevier Inc All rights of reproduction in any ... business key Consequently, we cannot guarantee that each business key points to one and only one object by defining a unique index on it Nor can we simply extend the scope of the index...

Ngày tải lên: 21/01/2014, 08:20

... significantly reduces the work involved in maintaining temporal data, and will eliminate the errors that would otherwise inevitably happen as temporal data is maintained Using a framework like the ... the taxonomy in terms of its topology On a line representing a timeline, we can place a line segment representing an episode We can also remove a line segment from that line Given a line seg...

Ngày tải lên: 21/01/2014, 08:20

... effective time it affects As a relationship between a point in time and a period of time, the basic options are that the point in time can be earlier than the period of time, within the period of time, ... integrity or a referential integrity constraint, it will reject that transaction In response, the AVF will stop processing the temporal transaction, undo Managing Time i...

Ngày tải lên: 21/01/2014, 08:20

... 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 Elsevier Inc All rights of reproduction in ... December 2012, into the indefinite future The first physical transaction step in this deletion is to withdraw versions and since each of them has at least one clock tick included in...

Ngày tải lên: 21/01/2014, 08:20