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15 Cards in this Set
- Front
- Back
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A two-dimensional table in which entries are single-valued, each field has a distinct name, and all the values are values of the same attribute (the one identified by the field name), the order of fields is immaterial, each row is distinct, and the order of rows is immaterial.
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Relation
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A collection of relations
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Relational Database
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A structure in which entries need not be single-valued but that satisfies all the other properties of a relation.
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Unnormalized relation
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A field name is qualified by preceding it with the table name and a period.
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Rep.RepNum
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The field or fields that uniquely identify a given row within the table.
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Primary Key
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A visual tool for manipulating relational databases. QBE queries are created by completing on-screen forms
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Query-By-Example (QBE)
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The theoretical method of manipulating relational databases.
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Relational algebra
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Relational algebra selects only certain rows from a table.
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SELECT
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Relational algebra selects only certain columns from a table.
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PROJECT
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Relational algebra combines data from two or more tables based on common columns.
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JOIN
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Relational algebra command that forms the union of two tables. For a union operation to make sense, the tables must be union compatible.
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UNION
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Relational algebra command forms the intersection of two tables.
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INTERSECT
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Relational algebra command forms the difference of two tables.
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SUBTRACT
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The _____ of two tables is the table obtained by concatenating every row in the first table with every row in the second table
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Product
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Relational Algebra process that divides one table by another table.
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Division
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