CS4482tut1a - followed by selecting only combinations of...

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Advanced Database Systems Tutorial 1 Are you ready to take this course on Advanced Database Systems? Test yourself 1. A superkey is a set of one or more attributes that allow us to identify uniquely a tuple in the relation. A minimal superkey (i.e., a superkey for which no proper subset is a superkey) is called a candidate key. A primary key is a candidate key that is chosen by the database designer as the principal means of identifying tuples within a relation. 2. A database consists of a number of files. A file is organized as a sequence of records. Records are mapped onto a number of disk blocks (4-8 KB are common block sizes). 3. It is costly to move many records as a result of a single insertion or deletion. One solution is to use overflow block but this requires file reorganization . 4. a) salary <75000 ( salary ( instructor )) salary ( salary <75000 ( instructor )) b) It is an equi-join which forms a Cartesian product of the two relations, r and s ,
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Unformatted text preview: followed by selecting only combinations of tuples satisfying r.A = s.B , where A and B are attributes or sets of attributes of relations r and s , respectively. 5. Atomicity : Either all operations of the transaction are reflected properly in the database, or none are. (Responsibility of the recovery system in the database system) Consistency : Execution of a transaction in isolation preserves the consistency of the database. (Responsibility of application programmers) Isolation : Even though multiple transactions may execute concurrently, the system guarantees that each transaction is unaware of other transactions executing concurrently in the system. (Responsibility of the concurrency-control system in the database system) Durability : After a transaction completes successfully, the changes it has made to the database persist, even if there are system failures. (Responsibility of the recovery system in the database system)...
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This note was uploaded on 01/11/2012 for the course CS CS4482 taught by Professor Drlee during the Winter '11 term at City University of Hong Kong.

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