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What is Schema and instances?
In DBMS,Schema is the overall Design of the Database.Instance is the information stored in the Database at a particular moment.In programming,you declare a variable which corresponds to "Schema".But its values changes as and when required which corresponds to "Instance". Google about levels of Database Abstraction. Physical Schema describes database design at physical level while a logical schema describes the database design at the logical level.A database may also have several schemas at the view level, sometimes called subschemas, that describe different views of the database.
What is schema instance?
In DBMS,Schema is the overall Design of the Database.Instance is the information stored in the Database at a particular moment.In programming,you declare a variable which corresponds to "Schema".But its values changes as and when required which corresponds to "Instance". Google about levels of Database Abstraction. Physical Schema describes database design at physical level while a logical schema describes the database design at the logical level.A database may also have several schemas at the view level, sometimes called subschemas, that describe different views of the database.
What is schema object of database?
We know that schema in the database is refer to the basic design of that database and is stored in an object . That object is known as schema object of database.
What is a database schema?
A database schema is described in a formal language supported by the database management system (DBMS). In a relational database, the schema defines the tables, the fields in each table, and the relationships between fields and tables. Schemas are generally stored in a data dictionary. Although a schema is defined in text database language, the term is often used to refer to a graphical depiction of the database structure Levels of database schema 1. Conceptual schema, a map of concepts and their relationships 2. Logical schema, a map of entities and their attributes and relations 3. Physical schema, a particular implementation of a logical schema 4. Schema object, Oracle database object 5. Schema is the over all structure of the database
What are the Types of database schema architecture?
The Star & Snowflake are two common type of database Schema.
How does one read a database schema?
One can easily read a database schema through any software available currently. Simpy because a database schema is a blueprint which can be read by a software.
What do you mean by logical schema in database?
tablespace,segment,extent,oracle blocks.. are the logical schema of a database
Data base state vs database schema?
The database schema is the description of the database. It defines how the database is set up and what data it is to contain and control. This description is given to the DBMS to manage the data. The database state is an image of how the database looks at any given time. The database schema is set unless you change how the database is structured. The database state will change whenever new data is entered into the database and the database is updated.
Difference between database schema and a database state in dbms?
The distinction between database schema and database state is very important. When we define a new database, we specify its database schema only to the DBMS. At this point, the corresponding database state is the empty state with no data. We get the initial state of the database when the database is first populated or loaded with the initial data. From then on, every time an update operation is applied to the database, we get another database state. At any point in time, the database has a current state. The DBMS is partly responsible for ensuring that every state of the database is a valid state-that is, a state that satisfies the structure and constraints specified in the schema. The DBMS stores the descriptions of the schema constructs and constraints-also called the meta-data-in the DBMS catalog so that DBMS software can refer to the schema whenever it needs to. The schema is sometimes called the intension, and a database state an extension of the schema.
What are predicates that define correct database states and relationship with in database?
schema
What is the difference between schema and database?
Database schema are the logical structure of entities (tables or object classes) and their relationships (keys, or object associations) in a database. Schema can exist at different levels of abstraction (see: en.wikipedia.org/wiki/Database_schema). Schema themselves may or may not exist as such in a database. In general schema at the higher levels of abstraction are design models that are captured in printed documents, and authored by business analysts and database designers, rather than created by database programmers and stored in the database itself. But in some types of databases, schema at any level of abstaction can be realized physically. In Oracle databases, schema can be realized as schema objects, which are a part of an Oracle database. These schema objects may represent a human user's conceptual model of the knowledge captured in an enterprise database. Thus defined, there can be many schema that can be associated with one physical database. In other kinds of relational database, an abstract user's schema can be represented by logically linked metadata, views, and stored procedures assocated with a user class. In object-oriented databases, especially those based on the highly self-referential language Smalltalk (e.g. Gemstone/S), schema are realized as "physical" objects in the database as a matter of course, as well as in the logical models captured in design documents. The schema objects in such databases are, in essence, the classes comprising the infrastructure of the database or application. Oracle-style user schema are readily created; these would be realized as user interface orchestrator classes.
What is the data schema in a database?
Logical Structure of database is know as database schema. All database entities are defined and relation between then is represented in structured way. It includes all constraints to be apply on each identity.
