Menu
When do we need to use a 1-to-1 relationship in database design? In my opinion, if two tables are in a 1-to-1 relationship, they can be combined into one table. Is this true?
499
In a one-to-many relationship, one record in a table can be associated with one or more records in another table. For example, each customer can have many sales orders.
Household One-to-One RelationshipsOne family lives in one house, and the house contains one family. One person has one passport, and the passport can only be used by one person. One person has one ID number, and the ID number is unique to one person. A person owns one dog, and the dog is owned by one person.
One-to-One relationship in DBMS is a relationship between an instance of an entity with another. An Employee is issued an Employee ID Card. An individual employee is offered a unique ID card in the company. Here, Employee and ID Card (ID_Card) are entities.
A mandatory relationship indicates that for every occurrence of entity A there must exist an entity B, and vice versa. When specifying a relationship as being mandatory one-to-one, you are imposing requirements known as integrity constraints.
Vertical partitioning for large tables to reduce I/O and cache requirements -- separate columns that are queried often vs rarely.
Adding a column to a production system when the alter table is "too expensive".
Super-type/subtype pattern.
Vertical partitioning to benefit from table (join) elimination -- providing optimizer supports it (again to reduce I/O and cache) .
Anchor modeling -- similar to 4, but down to 6NF.
101
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
