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What is a schema in a database context?

A schema is the logical design, structure, or blueprint of a database. It defines the organization of data, including how tables relate to each other, the data types for each column, constraints, and other structural elements. It's the metadata or 'data about data'.

What is an instance in a database?

An instance refers to the actual content or data stored in a database at a particular point in time. While the schema defines the structure, instances populate that structure with real values.

What is Data Definition Language (DDL)?

Data Definition Language (DDL) is a set of SQL commands used to define, modify, or delete database structures such as tables, indexes, and users. DDL commands deal with the database schema.

Key DDL commands include:

• CREATE: To create databases, tables, views, etc.
• ALTER: To modify the structure of existing database objects.
• DROP: To delete database objects.
• TRUNCATE: To remove all records from a table, including space allocated for the records.
• RENAME: To rename an existing database object.

Data Manipulation Language (DML) is a set of SQL commands used for managing data within schema objects. DML commands deal with the actual data (instances) in the database.

Key DML commands include:

• SELECT: To retrieve data from the database.
• INSERT: To add new data into a table.
• UPDATE: To modify existing data in a table.
• DELETE: To remove data