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Use of primary keys
less data redundancy
compatible with inconsistencies associated with database anomalies
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Why do you use Linq over SQL Statements?
The extensibility of the query architecture is used in the LINQ project itself to provide implementations that work over both XML and SQL data. The query operators over XML (LINQ to XML) use an efficient, easy-to-use, in-memory XML facility to provide XPath/XQuery functionality in the host programming language. The query operators over relational data (LINQ to SQL) build on the integration of SQL-based schema definitions into the common language runtime (CLR) type system. This integration provides strong typing over relational data while retaining the expressive power of the relational model and the performance of query evaluation directly in the underlying store.
What advantages does SQL have over relational algebra?
Generally relational models are queried using relational algebras. SQL and XQuery are examples of relational algebras, with XQuery actually being a purer form of a relational algebra. : XQuery :: + Already exists and supports this extended relational model :: + Supports XPath :: + Supported by Oracle, IBM and Microsoft databases :: + Existing open source implementations for those who don't have it :: - Not yet a standard (but probably will be) :: - Not very easy to formulate :: - Immature development bindings usually resulting in DOM manipulation (not very efficient) :: - Difficult language to optimize which may result in poor performance :: - No developer community :: - No developer tools :: - It's currently a read-only language and the update additions are not focused on transactional systems : SQL :: + Millions of developers know (and love) it :: + Most repositories already support it :: + Supports PROJECTION, JOIN and UNION :: + Long established standard :: + Efficient language bindings with JDBC and ODBC :: + Lots of development tools :: - Need to specify and implement HIERARCHY ENUMERATION :: - Need to work around the multi-value problem with PROJECTION and SELECTION functions
What advantage does a graph have over a table having same information in the form of numbers?
gsu
How do you use over as a preposition?
Use the word with a noun to define what it is over, or about. "He jumped over the fence." "The key is over the door." "They argued over the new tax plan."
Is over a verb?
Over is a preposition.
Which feature is uniquely found in an access layer switch within a hierarchical network model?
Power over Ethernet
What are the advantages of swot over six forces model analysis?
advantage of model analysis
What is precedence between relational operator and arithmetic operator?
Arithmetic operators (+, -, *, /, % ) have greater precedence over relational operators (<, >, <=, >=, ==, !=) in C language.
Advantages of a network database model over relational model?
Advantages:1. Network Model allows each record to have multiple parent and child relationships, unlike the hierarchical model which allows only one parent for each child. This forms a lattice like structure.Disadvantages:1. Companies like IBM chose to stick to the hierarchical models.2. As hardware speed improved, network models were replaced by more powerful models such as the relational model.
Which are the different Classification of database management systems?
Database ClassificationDatabase systems are classified according to the way they represent data, i.e., on their provided data model. Broadly speaking, data models are classified intorecord-oriented and object-oriented models. There are three standardized record-oriented data models, namely, hierarchical, network,and relational. Although there is not a single object-oriented data model standard, as we discussed in 5.1.1 Object Relational Models, there are two objected-based approaches: namely, object-relational and object-oriented. Let us summarize these models.Hierarchical Data ModelThe hierarchical model stores the data records in a tree structure with edges that connect the different records representing their relationships. Except for the root, all other nodes must have a parent node and each node may have either zero, or more child (dependent) records. Thus, in the hierarchical model, relationships between record types can be only one-to-one or one-to-many binary relationships.IBM's IMS is possibly the only hierarchical DBMS in use today. There are only a few places where it is being used. In IMS, many-to-many relationships are handled by storing the data in two trees with opposite dependencies. Recursive relationships are handled in the same way. This means that the database contains redundant data, which is a waste of space, which makes the database structure inflexible to data change, and which makes the update operations more complex. Basic referential integrity of parent-child relationship is enforced by the DBMS.The hierarchical model does not support declarative query processing. Retrievals are achieved through navigationembedded within a high-level programming language. The navigation is a tree pre-order traversal that starts from the root and proceeds down the tree, accessing the subtrees in order from left to right. This means that users know and operate directly on the physical schema. Hence, the hierarchical model supports a low level of abstraction compared to relational and object-oriented models, and it also offers only weak security and integrity.Network Data ModelThe network model is similar to the hierarchical one in that it eliminates data redundancy in a database by storing the data in a graph (or network) structure rather than in a tree structure. In this way, recursive and circular relationships, for example, can be expressed with edges connecting two records of the same type.The basic one-to-many relationship is represented by connecting the dependent records together in an ordered linked list with the parent record, which is called the owner, at the head of the list. Records are permitted to contain more than one link. This capability is used in expressing many-to-many binary relationships between two record types. Many-to-many relationships are expressed with the help of intermediate records that can be directly linked with records of both the related record types, providing an indirect link between these records. (The use of intermediate records is called decomposition.) Basic referential integrity constraints are enforced by the DBMS.Similar to the hierarchical data model, the network model does not provide for declarative query processing. Access to records is achieved by navigation through the network structure using a set of predefined commands. These one-record-at-a-time commands must be embedded in a general-purpose programming language. Unlike records in the relational model, records in the network model can have fields, which are either single value, called simpleattributes, or multi-valued, called vector attributes.Relational Data ModelIn the relational model, data is stored in tables that completely hide the physical organization of data. Thus, compared to the hierarchical and network models, the relational model supports a high level of abstraction and a flexible database structure. The database structure, i.e., the schema, can easily be changed to accommodate new data and new access requirements.Relationships of any cardinality (1:1, 1:N, and N:M) and degree (binary, recursive, or higher order) can be expressed by means of foreign keys that are logical pointers. Binary 1:1 and 1:N, and binary recursive relationships, can be expressed directly, whereas high-order and N:M relationships can be expressed by decomposition, i.e., with the use of an intermediate table.In addition to basic referential integrity, the relational model supports semantic integrity constraints by means of checks, assertions, and triggers.Finally, as we have discussed in some detail, the relational model supports declarative, interactive query languages such as SQL and QBE. Furthermore, it can be embedded in almost any programming language, and therefore it supports the development of database application programs.Object-Oriented Data ModelThe object-oriented model supports a high level of abstraction and exhibits the same flexibility in specifying data relationships as the relational model. Relationships in the object-oriented model are expressed as references to object IDs. However, the object-oriented model offers more flexibility in specifying the schema of the database by means of complex types, user-defined types, user-defined functions, and object inheritance.Unlike the object-relational model, object-oriented data models are strongly tied to an object-oriented programming language (such as C++ and Smalltalk) acting as their data manipulation language. (In this respect, object-oriented models resemble the hierarchical and network models.) The object-oriented language is extended to support persistent objects whose values are stored in the database and can be shared with other programs. By manipulating transient and persistent objects uniformly, object-oriented models eliminate the so-called impedance mismatch; that is, object-oriented models can thus eliminate any incompatibility between the declarative database manipulation language and the procedural application programming language that is due to difference in programming paradigms and type systems. Thus, object-oriented databases simplify the task of programming by supporting a single level storage and a computationally complete DDL/DML.In order to support declarative and interactive query processing, the ODMG standardization treats the object-relational model as a special object-oriented model, implementing its declarative query language.
What is an example of an access relational database?
There is no such thing as an 'Access' Relational Database.A Relational Database Management System is one that has been built to deliver the requirements set out by Edgar Codd in 1970 such that the functions provided by the software conform to relational algebra. This means that the validity actions of the database management system over the data contained in it can be modeled and proved on a mathematical basis.Oracle, DB2, SQL Server, MySQL, etc. all implement most of the requirements of Codd's paper.It is worth noting that the relational model is the ONLYone where the affects of putting data in it can be proven.
What was not a major advantage of Copernicus' Sun-centered model over the Ptolemaic model?
It made significantly better predictions of planetary positions in our sky.
What is the difference between relational tuple calculus and domain calculus?
Relational tuple calculus has its variables range over tuples, where domain relational calculus ranges its variables over the field values, or domain elements. Both types of calculus are subsets of first order logic.
What are the main differences between relational algebra and relational calculus?
Relation algebra is a procedural language where relation calculus is non-procedural languageRelational algebra, an offshoot of first-orderlogic (and of algebra of sets), deals with a set of finitaryrelations (see also relation (database)) which is closed under certain operators. These operators operate on one or more relations to yield a relation. Relational algebra is a part of computer science.Relational calculus consists of two calculi, the tuplerelational calculus and the domain relational calculus, that are part of the relational model for databases and provide a declarative way to specify database queries. This in contrast to the relational algebra which is also part of the relational model but provides a more procedural way for specifying queries.The relational algebra might suggest these steps to retrieve the phone numbers and names of book stores that supply Some Sample Book:1. Join books and titles over the BookstoreID.2. Restrict the result of that join to tuplesfor the book Some Sample Book.3. Project the result of that restriction over StoreNameand StorePhone.The relational calculus would formulate a descriptive, declarative way:Get StoreNameand StorePhonefor supplies such that there exists a title BK with the same BookstoreIDvalue and with a BookTitlevalue of Some Sample Book.The relational algebra and the relational calculus are essentially logically equivalent: for any algebraic expression, there is an equivalent expression in the calculus, and vice versa.This result is known as Codd'stheorem
What are the advantages of rdbms over dbms?
RDBMS is a Relational Data Base Management System Relational DBMS. This adds the additional condition that the system supports a tabular structure for the data, with enforced relationships between the tables. This excludes the databases that don't support a tabular structure or don't enforce relationships between tables.
Major advantage of Copernicus' Sun-centered model over the Ptolemaic model?
It offered more natural explanation for the apparent retrograde motion of planets in our sky.
Why would a designer choose a flat network over a hierarchical?
A designer Êwould Êchoose a flat network over a hierarchical because Êit is cheap to implement, maintain and administrate.ÊÊItÊis designed toÊreduceÊ the number of routers and switches on Êa computerÊnetwork.
