overall design of the database
Physical schema,logical schema and sub schemas
It is the number of attribute of its relation schema. Its is an association among two or more entities..
The schema is the physical arrangement of the data as it appears in the DBMS. The subschema is the logical view of the data as it appears to the application program.
The schema is the physical arrangement of the data as it appears in the DBMS. The sub-schema is the logical view of the data as it appears to the application program.
SCHEMA is the physical arrangement of the data as it appears in the DBMS. SUB-SCHEMA is the logical view of the data as it appears to the application program.
the overall logical data base description is referred to as a schema. it is sometimes also referred to as an overall modal of the data, a conceptual modal of the data, a conceptual schema
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.
A Database has three views. The External Schema: What the end user sees. The Internal Schema: What the programmers of the program see. The Conceptual Schema: The basic plan of the database. Most of the time this is in paper form as a Conceptual Schema Diagram (CSD)
difference between relation sehema and relation instance in dbms
what do u mean by lossiess join in dbms
Data is represented/organized in a dbms in the form of Schemas, tables, rows and columns One DBMS may have multiple Schemas One Schema may have multiple tables One table may have multiple rows One row may have multiple columns If these tables are related to one another it forms a RDBMS - A Relational DBMS
As I understand it, a database schema is a physical entity, it describes the structure of exactly how the data is stored and is itself stored by DBMS for reference. Data model, on the other hand, is an abstract representation of database.