What are the three types of associations, and which is the most commonly used? Binary, unary, ternary. Binary is most common.

Multiplicity actually consists of two separate constraints known as cardinality and participation. Cardinality describes the number of possible relationships for each participating entity. Participation determines whether all or only some entity occurrences participate in a relationship.

Describe what the multiplicity constraint represents for a relationship type. It represents the number (or range) of possible occurrences of an entity type that may relate to a single occurrence of an associated entity type through a particular relationship. What are enterprise constraints?

Referential integrity is important, because it keeps you from introducing errors into your database. Suppose you have an Order Parts table like the following. Part number and order number, each foreign keys in this relation, also form the composite primary key. Such a situation shows a loss of referential integrity.

A Foreign Key is a database key that is used to link two tables together. The FOREIGN KEY constraint identifies the relationships between the database tables by referencing a column, or set of columns, in the Child table that contains the foreign key, to the PRIMARY KEY column or set of columns, in the Parent table.

Turn referential integrity on or off

1. On the Database Tools tab, in the Relationships group, click Relationships.
2. On the Design tab, in the Relationships group, click All Relationships.
3. Click the relationship line for the relationship that you want to change.
4. Double-click the relationship line.

When you create a relationship between two tables, it is usually a good idea to enforce referential integrity. Referential integrity keeps data accurate and ensures that you don’t accidentally change or delete related data in one table but not in the other.

SQL joining through referential integrity

1. A REFERENTIAL INTEGRITY is a database concept that is used to build and maintain logical relationships between tables to avoid logical corruption of data.
2. Usually, referential integrity is made up of the combination of a primary key and a foreign key.

A one-to-many relationship is the most common type of relationship. In a one-to-many relationship, a record in Table A can have many matching records in Table B, but a record in Table B has only one matching record in Table A.

three types

There are three types of relationships that can exist between two entities.

• One-to-One Relationship.
• One-to-Many or Many-to-One Relationship.
• Many-to-Many Relationship.