Robin Burden answered
A schema is usually the term used to describe a database management system's (DBMS) plan or formulation, whereas a sub-schema is usually a sub-division of this generalized structure.
Their use is meant to improve ease of access to tables and data in a database, in accordance with the relational database model.
What's a schema in DBMS?
In simple terms, a schema is the design or layout of a database management system. It will often have a list of units or entities that feature in the database, and describe the relationships between them.
A schema often remains unchanged, despite the volatile nature of a database. It is essentially the framework through which parts of a database are contextualized.
What is a sub-schema?
A sub-schema is best described as the way that the data in a DBMS appears when viewed by an application or a user. The most important criteria for a sub-schema is that it appears logically, and as part of a decipherable system.
This is not always the case with a schema itself.
The whole DBMS model of using a schema and sub-schema is based on the relational database management system concept first developed by IBM.
Their use is meant to improve ease of access to tables and data in a database, in accordance with the relational database model.
What's a schema in DBMS?
In simple terms, a schema is the design or layout of a database management system. It will often have a list of units or entities that feature in the database, and describe the relationships between them.
A schema often remains unchanged, despite the volatile nature of a database. It is essentially the framework through which parts of a database are contextualized.
What is a sub-schema?
A sub-schema is best described as the way that the data in a DBMS appears when viewed by an application or a user. The most important criteria for a sub-schema is that it appears logically, and as part of a decipherable system.
This is not always the case with a schema itself.
The whole DBMS model of using a schema and sub-schema is based on the relational database management system concept first developed by IBM.