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8 Cards in this Set
- Front
- Back
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SELECT OPERATOR Define: Select Operator what is the format? |
Selects row that satisfies the condition Format: σ condition (relation) |
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SELECT OPERATOR Write the select operator for: From person, select row where hobby is hockey. |
σ hobby = 'hockey' (Person) |
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SELECT OPERATOR Are these correct uses of selection conditions? σ id > 1000 OR hobby = 'hockey' (Person) σ id > 3000 AND id < 3500 (Person) σ NOT(hobby = 'hockey') (Person) |
Yes Yes Yes |
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PROJECT OPERATOR Define: Project operator |
This specifies what information is projected to the output. Format: π attribute list (relation) |
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PROJECT OPERATOR Project the name and hobby from Person |
π name, hobby (Person) |
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EXPRESSION EXAMPLE What would be the output? |
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When are two relations compatible for union |
1. Both have same number of columns 2. Name of attributes are the same |
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Remember this |
lol |
