Schema
Here, the database design is referred to as the DBMS schema. As an illustration, let's consider the employee table. The attributes listed below are found in the employee table. These characteristics include EMP_ID, EMP_ADDRESS, EMP_NAME, and EMP_CONTACT. The employee table's schema is as follows.
Types of schema
Schema is further divided into three types. These three are as follows:
- Logical schema
- View schema
- Physical schema
In DBMS, the schema is displayed as a diagram.
We are able to understand the connections among the information found in the database. We may use this schema to implement DBMS functions like update, insert, remove, and search.
The logical perspective of the database is defined by the schema. It sheds some light on the database and what information should be stored in which locations.
1. Physical Schema
The database is designed at the physical level in the physical schema. The schema at this level explains the management and storage of the data block.
2. Logical Schema
At the logical level, it is a database architecture. Utilizing logical structure, programmers create apps.
3. External Schema
View-level schema is involved. It is a schema's top level that establishes end users' perspectives.
One physical schema, one logical schema, and multiple sub or external schemas are often supported by the Database Management System (DBMS).
The structure and design of the database where the data will be kept are referred to as the database schema. Unless otherwise changed, it is the only thing that doesn't change. It specifies the format, kind, and method of storing the data.
Instance
A collection of data that is stored in a database at a specific time is referred to as an instance, extension, or database state. The data kept in the database at a specific moment is referred to as the database instance. As a result, it is a dynamic value that is always shifting.
Example
User1, emai.com, 11345679, and address are examples of database instances for the Person database. As a result, the person construct will include each of their distinct entities in the characteristics referred to as instances. This is seen below-
Person
| Name | Phone no. | |
| Jacky | jk12@Ysdb.com | 9786548787 |
| Kartik | kartik@sdbf.com | 8654987776 |
| Manvi | Mannuu237@.com | 8976897456 |
Mapping
The process of establishing the connections between various data models or levels of abstraction within a database is known as mapping in a database management system (DBMS).
Types of Mapping
1. Conceptual to logical mapping
In this process, a logical schema (such as a relational model) is created by using a high-level conceptual schema (such as an entity-relationship model). It specifies the representation of entities, characteristics, and relationships in the database.
2. Logical to physical mapping
This is the process by which the logical schema is turned into a physical schema. It involves specifying the file formats, indexing strategies, and data types that are used to store data in the database.
3. Data mapping
This method, which is frequently applied in data integration and data warehousing, involves connecting various data sources. It highlights the relationships between data from one source and data from another
4. Object-relational mapping
ORM frameworks are used in application development to translate programming language objects to database tables. This enables developers to use high-level programming constructs instead of SQL queries to communicate with the database.
5. Schema mapping
In systems that combine several databases or data sources, this involves establishing the relationships between various database schemas.
