SWEN 220- Midterm Exam Guide - Comprehensive Notes for the exam ( 17 pages long!)
6 Oct 2017
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For that set of columns, if there is a single duplicate, then it is no longer a superkey. Superkey, if there are no duplicates it is valid. Candidate keys are superkeys but the minimal state (only unique column) usually only one column. Primary key will be one of your candidate keys. Alternate key will be the other candidate keys that isn"t the primary key. Surrogate key is something that is generated to guarantee uniqueness and a primary key. Foreign key is used to pair between two databases. A foreign key must exist, or else it"s invalid. Subtract the second dataset from the first dataset. {1,2} x {3,4} = { (1,3), (1,4), (2,3), (2,4) } Removes or keeps a specific subset of the dataset. Selects from a table based on an attribute. Selects from a table and then renames the attributes accordingly combines two tables on a common column. Table that contains the both of two other tables.
