Topic: database keys and indexing

topics > computer science > database > Group: database model

database implementation
database queries, joins, and relational algebra
database schema
entity-relationship database model
external search and sort
hash table and hash functions
full-text indexing
relational database
sort algorithms
Subtopic: database key up

Quote: a database uniquely identifies every object [»coddEF_1990]
Quote: the primary key plus table name uniquely identifies every row of a relational database; integrity is not enforced by other models [»coddEF_1990]
Quote: a primary key is one or more domains that uniquely identifies tuples of a relation [»coddEF6_1970]
Quote: the same data value in a database could be a primary key or could be a secondary key specifying a set of records [»bachCW11_1973]
Quote: data in relational database addressed by relation name, attribute name, and primary key [»coddEF2_1982]
Quote: the relational model uses user-defined and user-controlled primary keys as unique and permanent identifiers
Quote: an Agenda item acts like a unique key and a category corresponds to an indexed, non-key field
QuoteRef: chenPP3_1976 ;;14 "Basically, an entity key is a group of attributes such that the mapping from the entity set to the corresponding group of value sets is one-to-one

Subtopic: foreign key up

Quote: a foreign key refers to a row of another table via a value from the same domain as the primary key [»coddEF_1990]
Quote: a foreign key consists of values for the primary key of a relation [»coddEF6_1970]
Quote: foreign keys blur the distinction between entities and relations
Quote: referential integrity if every foreign key refers to a primary key unless marked as a missing values [»coddEF_1990]

Subtopic: hash joins up

Quote: criss-cross hash joins interleaves zoned partitions configured through page maps; low memory and I/O costs; even better if ordered [»gopaRD7_2001]

Subtopic: B-tree up

Quote: B-trees widely used to implement relational database systems; primary commercial application [»bayeR_2002]

Subtopic: integrity constraint up

Quote: integrity constraints checked automatically, no voluntary action; concern of the community of users [»coddEF_1990]

Subtopic: problems with keys up

Quote: soft keys can be null; merging soft keys propagates softness to all keys [»kentW1_1984]
Quote: problems with user-controlled keys as permanent surrogates: can be changed, different keys for same entity, entities without keys
Quote: with user-controlled keys, an equi-join on common key values may be different that a join on common entities

Related Topics up

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Topic: database implementation (18 items)
Topic: database queries, joins, and relational algebra (33 items)
Topic: database schema (29 items)
Topic: entity-relationship database model (21 items)
Topic: external search and sort (23 items)
Topic: hash table and hash functions (41 items)
Topic: full-text indexing (35 items)
Topic: relational database (34 items)
Topic: sort algorithms
(24 items)

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