6 Database Management
In database design, the cardinality or fundamental principle of one data aspect with respect to another is a critical feature. The relationship of one to the other must be precise and exact between each Codd's steps for organizing database tables and their keys is called database normalization, which avoids certain hidden. All are drawn from the Elephind newspaper database. The earliest figurative use of "low key" is from "A Musical Definition," in the [Leesburg. A primary key in a file is the field (or fields) whose value identifies a record These data models define the logical relationships among the data elements.
A common example is storing materialized views, which consist of frequently needed external views or query results. Storing such views saves the expensive computing of them each time they are needed. The downsides of materialized views are the overhead incurred when updating them to keep them synchronized with their original updated database data, and the cost of storage redundancy.
Database replication Occasionally a database employs storage redundancy by database objects replication with one or more copies to increase data availability both to improve performance of simultaneous multiple end-user accesses to a same database object, and to provide resiliency in a case of partial failure of a distributed database.
Updates of a replicated object need to be synchronized across the object copies. In many cases, the entire database is replicated. Security[ edit ] This article appears to contradict the article Database security. Please see discussion on the linked talk page.
March Main article: Database security Database security deals with all various aspects of protecting the database content, its owners, and its users. It ranges from protection from intentional unauthorized database uses to unintentional database accesses by unauthorized entities e.
Database access control deals with controlling who a person or a certain computer program is allowed to access what information in the database. The information may comprise specific database objects e. Database access controls are set by special authorized by the database owner personnel that uses dedicated protected security DBMS interfaces.
This may be managed directly on an individual basis, or by the assignment of individuals and privileges to groups, or in the most elaborate models through the assignment of individuals and groups to roles which are then granted entitlements. Data security prevents unauthorized users from viewing or updating the database. Using passwords, users are allowed access to the entire database or subsets of it called "subschemas".
For example, an employee database can contain all the data about an individual employee, but one group of users may be authorized to view only payroll data, while others are allowed access to only work history and medical data.
If the DBMS provides a way to interactively enter and update the database, as well as interrogate it, this capability allows for managing personal databases. Data security in general deals with protecting specific chunks of data, both physically i. Change and access logging records who accessed which attributes, what was changed, and when it was changed.
Logging services allow for a forensic database audit later by keeping a record of access occurrences and changes.
Sometimes application-level code is used to record changes rather than leaving this to the database. Monitoring can be set up to attempt to detect security breaches.
Transactions and concurrency[ edit ] Further information: Concurrency control Database transactions can be used to introduce some level of fault tolerance and data integrity after recovery from a crash. A database transaction is a unit of work, typically encapsulating a number of operations over a database e.9 Low Key Signs That He Actually Likes You - Rules Of Relationship
The acronym ACID describes some ideal properties of a database transaction: However, in some situations, it is desirable to move, migrate a database from one DBMS to another.
The migration involves the database's transformation from one DBMS type to another. The transformation should maintain if possible the database related application i. Thus, the database's conceptual and external architectural levels should be maintained in the transformation. It may be desired that also some aspects of the architecture internal level are maintained.
A complex or large database migration may be a complicated and costly one-time project by itself, which should be factored into the decision to migrate. This in spite of the fact that tools may exist to help migration between specific DBMSs. Building, maintaining, and tuning[ edit ] Main article: Database tuning After designing a database for an application, the next stage is building the database.
Typically, an appropriate general-purpose DBMS can be selected to be used for this purpose. A DBMS provides the needed user interfaces to be used by database administrators to define the needed application's data structures within the DBMS's respective data model. Other user interfaces are used to select needed DBMS parameters like security related, storage allocation parameters, etc.
When the database is ready all its data structures and other needed components are definedit is typically populated with initial application's data database initialization, which is typically a distinct project; in many cases using specialized DBMS interfaces that support bulk insertion before making it operational. In some cases, the database becomes operational while empty of application data, and data are accumulated during its operation.
Is Your Relationship Low-Key Or On the Down Low?
After the database is created, initialised and populated it needs to be maintained. Various database parameters may need changing and the database may need to be tuned tuning for better performance; application's data structures may be changed or added, new related application programs may be written to add to the application's functionality, etc. Backup and restore[ edit ] Main article: Backup Sometimes it is desired to bring a database back to a previous state for many reasons, e.
To achieve this, a backup operation is done occasionally or continuously, where each desired database state i. When this state is needed, i.
Cardinality (data modeling)
Static analysis[ edit ] Static analysis techniques for software verification can be applied also in the scenario of query languages. The abstraction of relational database system has many interesting applications, in particular, for security purposes, such as fine grained access control, watermarking, etc. Other DBMS features might include: Database logs — This helps in keeping a history of the executed functions. Graphics component for producing graphs and charts, especially in a data warehouse system.
Query optimizer — Performs query optimization on every query to choose an efficient query plan a partial order tree of operations to be executed to compute the query result. May be specific to a particular storage engine.
Tools or hooks for database design, application programming, application program maintenance, database performance analysis and monitoring, database configuration monitoring, DBMS hardware configuration a DBMS and related database may span computers, networks, and storage units and related database mapping especially for a distributed DBMSstorage allocation and database layout monitoring, storage migration, etc.
Increasingly, there are calls for a single system that incorporates all of these core functionalities into the same build, test, and deployment framework for database management and source control. Borrowing from other developments in the software industry, some market such offerings as " DevOps for database".
Database design The first task of a database designer is to produce a conceptual data model that reflects the structure of the information to be held in the database. A common approach to this is to develop an entity-relationship model, often with the aid of drawing tools. Another popular approach is the Unified Modeling Language. A successful data model will accurately reflect the possible state of the external world being modeled: Designing a good conceptual data model requires a good understanding of the application domain; it typically involves asking deep questions about the things of interest to an organization, like "can a customer also be a supplier?
The answers to these questions establish definitions of the terminology used for entities customers, products, flights, flight segments and their relationships and attributes. Producing the conceptual data model sometimes involves input from business processesor the analysis of workflow in the organization.
This can help to establish what information is needed in the database, and what can be left out. For example, it can help when deciding whether the database needs to hold historic data as well as current data.
Attractive as the origin story implicating the lower keys of the organ and likewise the lower, or white, keys of the piano in the development of use of 'low key' in the later figurative sense of "not elaborate, showy, or intense; muted, restrained; modest" OED, low key, fig. Simply, 'low key' in the specific figurative sense at hand is intrinsically comparative, and developed from the correlated comparative phrase 'lower key'.
For its part, 'lower key', as used in the later figurative sense, first to the best of my knowledge appeared in two primary contexts in the mids: The latter, rhetoric, is in this case an element of religious persuasion by means of the ornamentation of speech or writing, and so partakes so much of the former, the religious context, that the two, although I have here artificially separated them, are perhaps but one context.
The evidence supporting my conclusion is, like the phrase derivation itself, simple and straightforward. Very early uses of 'lower key', and subsequent uses in the intervening years between those early uses and later uses such as those cited by OED from and after, are in the specific figurative sense OED sense 2 of 'low-key'. By this strain of rhetorick Chrysostome as his manner is perswadeth the people to come to the Lords Table with no lesse reverence, than if they were to receive a fiery coal as Esay did in his vision from one of the glorious Seaphims.
Chrysostome had no intent that the bread was transubstantiated, no more than that the Priest was changed into an Angel, or his hand into a pair of tongs, or the body of Christ into a coal of fire; and he useth the same amplification in both the speeches, the same phrase [think you] and at the same time, and to the same people: Sixtus Senensis gives a good rule for interpretation of the Fathers speeches, specially in this argument; z The sayings of Preachers are not to be urged in that rigour of their words; for after the manner of Orators, they use to speak many times hyperbolically, and in exesse.
Now these and the like sayings must be favourably construed, as being improper speeches, rhetoricall strains, purposely uttered to move affections, stirre up devotion, and bring the Sacrament out of contempt, that so the Communicants eyes may not be finally fixed on the outward elements of bread and wine Computers must keep track of the storage location of each record using a variety of direct organization methods so that data can be retrieved when needed.
New transactions' data do not have to be sorted. Processing that requires immediate responses or updating is easily performed. The database stores not only the values of the attributes of various entities but also the relationships between these entities.
A database is managed by a database management system DBMSa systems software that provides assistance in managing databases shared by many users. Helps organize data for effective access by a variety of users with different access needs and for efficient storage. It makes it possible to create, access, maintain, and control databases. Through a DBMS, data can be integrated and presented on demand.
Advantages of a database management approach: Avoiding uncontrolled data redundancy and preventing inconsistency 2. Flexible access to shared data 4. Advantages of centralized control of data 6.
Etymology of the term "low key" - English Language & Usage Stack Exchange
These data models define the logical relationships among the data elements needed to support a basic business process.
A DBMS serves as a logical framework schema, subschema, and physical on which to base the physical design of databases and the development of application programs to support the business processes of the organization. A DBMS enables us to define a database on three levels: Schema - is an overall logical view of the relationships between data in a database. Subschema - is a logical view of data relationships needed to support specific end user application programs that will access the database.
Physical - looks at how data is physically arranged, stored, and accessed on the magnetic disks and other secondary storage devices of a computer system. It also provides a language for manipulating the data, called the data manipulation language DMLwhich makes it possible to access records, change values of attributes, and delete or insert records.