Practise vocabulary for ER modelling: entities, attributes, relationships, cardinality, and ERD notation.
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In ER modelling, a ___ represents a real-world object or concept about which data is stored — for example, Customer or Order.
An entity is a distinct object type about which data is stored. In the relational model, entities become tables. Each row in the table represents an entity instance.
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___ describes the number of entity instances that can participate in a relationship — for example, one-to-many or many-to-many.
Cardinality defines the numerical relationship between entities: 1:1 (one customer has one loyalty account), 1:N (one customer has many orders), M:N (many students take many courses).
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A many-to-many relationship between two entities is typically implemented in a relational database using a ___ table.
A junction (bridge) table resolves M:N relationships by adding a new table with foreign keys to both entities. For example, Order_Product bridges Orders and Products with quantity as an attribute.
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A ___ key uniquely identifies each row in a table and cannot contain NULL values.
A primary key uniquely identifies each row. It must be unique across all rows and cannot be NULL. It can be a single column (surrogate key) or a combination of columns (composite primary key).
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A ___ key in a table is a column (or set of columns) that references the primary key of another table, enforcing referential integrity.
A foreign key creates a link between two tables by referencing the primary key of the parent table. The database enforces referential integrity — you cannot insert a foreign key value that doesn't exist in the referenced table.