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36 Cards in this Set
- Front
- Back
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relation schema
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logical design of a relation, contains relation name, list of attributes, and their domains
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relation
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the entire set of data that is possible for a relation where the values of each tuple are logically related and conform to the proper domains
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relation instance
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the set of tuples that actually exist in a relation at a given time
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tuple
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the unordered set of related attribute values for a particular relation
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attribute
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unordered attribute name and domain
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domain
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permitted set of values corresponding to data types and other constraints
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value
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a specific value conforming to the domain of an attribute, must be atomic
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atomic
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indivisible, not composite
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super key
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one or more attributes in a relation which can uniquely identify the tuple in which they appear for each and every tuple in the relation
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candidate key
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a minimal super key, no attributes are in the key that do not help identify the tuple
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primary key
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a candidate key which is chosen to be the primary means of identifying tuples in a relation
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foreign key
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the primary key of one relation included in another relation
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referential integrity
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the value of a foreign key in the referencing relation much appear as a primary key value in the references relation
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constraint
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values stored much satisfy certain limitations, such as domain, referential integrity, assertions, and authorization
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relational algebra
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a set of operations that take one or more relation as input and return a relation as output
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join
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the merging of two relations where pairs of tuples, one from each relation, are combined to form one tuple
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Cartesian/cross product
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every tuple in a relation is combined with every tuple of another relation
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natural join
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tuples in a relation are combined with tuples in another relation where the values match on all attributes having the same name
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outer join
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returns all tuples from the outer side of a join whether they match with a tuple on the other side or not
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selection
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returns tuples of the input relation that satisfy a predicate
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projection
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return specified attributes from all tuples, removing duplicates
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union
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all the tuples from a relation are appended with all tuples from another relation
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except/minus/difference
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all tuples in a relation not appearing in another relation
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intersect
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all tuples in a relation r1 that also appear in a relation r2
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symmetric difference
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all tuples in r1 and r2 except the ones that appear in both
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database schema
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logical design and structure of a database, table definitions
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relational database
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the collection of tables
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database instance
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snapshot of all data in the tables of a database at a specific point in time
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table
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a visual/physical representation of a relation, made of a heading (columns) and a body (rows), collection of rows
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columns
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correspond to attributes in a relation schema, are ordered, may be unnamed, and may have duplicates
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rows
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represents a set of related data values, are ordered, each row in a table has the same structure
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entity
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represents a thing or object in the real world that is distinguishable from all other objects, must be unique based on the value of its attributes, no duplicates allowed
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entity set
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set of entities of the same type that share the same properties
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entity attributes
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descriptive properties possessed by each member of an entity set, each entity has a value for each of its attributes
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relationship
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association among several entities, deals with particular instances/entities
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relationship set
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a set of relationships of the same type, each relationship in the set much be unique, attributes of a relationship set are the primary key attributes of each of the entity sets that are being related
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