Data Definition Language (DDL) is used to define and manage the structure of a database, including creating, altering, and dropping tables and schemas.

Boyce-Codd Normal Form (BCNF) is a higher normal form that ensures every determinant in the database is a candidate key, addressing certain types of anomalies that 3NF does not.

In ER diagrams, a child entity inherits attributes and relations from a parent entity, often representing a subclass or specialized entity.

B-tree indexes are typically used to improve the speed of queries that involve range searches because they maintain the sorted order of data. This makes it efficient to search for a range of values, as the B-tree structure allows for quick navigation to the starting point of the range and sequential access to the subsequent entries.

To ensure ACID (Atomicity, Consistency, Isolation, Durability) properties are maintained in a transaction, it is essential to use the transaction management features provided by the database management system. These features ensure that all operations within a transaction are completed successfully and consistently, even in the event of a failure.

The definition of a database schema, which includes the structure of the tables, fields, and relationships, is stored in the database management system's metadata. This metadata provides a blueprint for how data is organized and accessed within the database.

A database is in the Third Normal Form (3NF) if it is in the Second Normal Form (2NF) and all its attributes are functionally dependent only on the primary key, meaning there are no transitive dependencies. This helps to further reduce data redundancy and maintain data integrity.

The primary purpose of normalization is to reduce data redundancy and eliminate undesirable characteristics like insertion, update, and deletion anomalies. By organizing data into tables and defining relationships between them, normalization ensures that each piece of data is stored only once.