of the most valuable artifacts that a data team can deliver to the business. Explain why the data dictionary is sometimes called "the
A data dictionary is a description of all tables in the
Explain why the data dictionary is sometimes called "the database designer's database."
In a database context, what are homonyms and synonyms and why should they be avoided?
In database design, the information are stored in various tables. Entity and referential integrity relates to the integrity of these tables individually and in relation.
Entity Integrity
Entity integrity is the mechanism that makes sure that every table has a primary key. The primary keys are the unique values for each row of a table and acts as a unique identifier for the table. There needs to be two constraints which must be satisfied for a primary key. They are
Primary key is unique for a row
Primary key is not null value
This means that the primary key must exist for each of the record entries on the row and must be unique at all time.
Referential Integrity
Referential integrity is the mechanism that defines the existence and operation of a foreign key. A foreign key on a table must always refer to an existing primary key from another table. The constraint for the existence of a foreign key is
A valid foreign key must always refer to an existing primary key
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