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
The three main parts of a database structure are the database schema, the data, and the database management system (DBMS). The schema defines the organization and structure of the data, including tables, relationships, and constraints. The data consists of the actual information stored within the database, organized according to the schema. The DBMS is the software that facilitates the creation, manipulation, and management of the database, enabling users to perform operations such as querying and updating the data.
what do u mean by lossiess join in dbms
A database schema can be written by a programmer or generated through a DBMS utility program. This schema defines the structure of a database, including tables, fields, data types, and relationships. Additionally, SQL queries for data manipulation and retrieval may also be crafted by programmers or produced using built-in query builders in a DBMS. These tools facilitate efficient database management and interaction.