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| {{Unreferenced|date=March 2007}}
| | 29 year old Light Technician Tod Jernigan from Baie-Comeau, has many pursuits which include leathercrafting, como ganhar dinheiro na internet and tombstone rubbing. Recollects what an amazing place it was having paid checking out the City of Vicenza and the Palladian Villas of the Veneto.<br><br>my blog: [http://www.comoganhardinheiro101.com/como-ganhar-dinheiro-pela-internet/ ganhando dinheiro na internet] |
| In [[relational algebra]], a '''rename''' is a [[unary operation]] written as <math>\rho_{a/b}(R)</math> where:
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| * <math>R</math> is a [[Relation (mathematics)|relation]]
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| * <math>a</math> and <math>b</math> are [[Property|attribute]] names
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| * <math>b</math> is an [[Property|attribute]] of <math>R</math>
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| The result is identical to <math>R</math> except that the <math>b</math> attribute in all [[tuple]]s is renamed to <math>a</math>. For an example, consider the following invocation of <math>\rho</math> on an <math>Employee</math> relation and the result of that invocation:
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| {| align="center" cellpadding="0" cellspacing="20"
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| ! <math>Employee</math>
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| ! <math>\rho_{EmployeeName/Name}(Employee)</math>
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| |- style="vertical-align: top"
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| {| align="center" border="0" cellpadding="5" cellspacing="0" style="border-collapse: collapse; border: 1px solid black"
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| |- style="background-color: silver; text-align: left"
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| ! style="border: 1px solid black" | Name
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| ! style="border: 1px solid black" | EmployeeId
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| | style="border: 1px solid black" | Harry
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| | style="border: 1px solid black" | 3415
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| |-
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| | style="border: 1px solid black" | Sally
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| | style="border: 1px solid black" | 2241
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| |}
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| {| align="center" border="0" cellpadding="5" cellspacing="0" style="border-collapse: collapse; border: 1px solid black"
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| |- style="background-color: silver; text-align: left"
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| ! style="border: 1px solid black" | EmployeeName
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| ! style="border: 1px solid black" | EmployeeId
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| |-
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| | style="border: 1px solid black" | Harry
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| | style="border: 1px solid black" | 3415
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| |-
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| | style="border: 1px solid black" | Sally
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| | style="border: 1px solid black" | 2241
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| |}
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| |}
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| Formally the semantics of the rename operator is defined as follows:
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| : <math>\rho_{a/b}(R) = \{ \ t[a/b] : t \in R \ \}</math>
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| where <math>t[a/b]</math> is defined as the tuple <math>t</math> with the <math>b</math> attribute renamed to <math>a</math> so that:
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| : <math>t[a/b] = \{ \ (c, v) \ | \ ( c, v ) \in t, \ c \ne b \ \} \cup \{ \ (a, \ t(b) ) \ \}</math>
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| {{DEFAULTSORT:Rename (Relational Algebra)}}
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| [[Category:Relational algebra]]
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29 year old Light Technician Tod Jernigan from Baie-Comeau, has many pursuits which include leathercrafting, como ganhar dinheiro na internet and tombstone rubbing. Recollects what an amazing place it was having paid checking out the City of Vicenza and the Palladian Villas of the Veneto.
my blog: ganhando dinheiro na internet