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Tài liệu Database Systems: The Complete Book- P1 doc

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Tài liệu Database Systems: The Complete Book- P5 pptx

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... happens if there is a failure after line (14); perhaps the computer fails or the network connecting the database to the processor that is actually performing the transfer fails. Then the database ... stdo has the value "Disney" and yr has the value 1990, then the result of the select-from is the bag of the lengths of the movies made by Disney in 1990. When we apply the SUM operator ... If the transaction aborts, then (without precautions) it is possible that these changes were seen by some other transaction. The most common solution is for the database system to lock the...

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Tài liệu Database Systems: The Complete Book- P6 docx

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... doubled the size of blocks. tre n-ould halve the number of disk 110's for an algorithm like TPAIJIS. On the other hand, the only change in the time to access a block would be that the transfer ... and the three gaps between them. Recall that the gaps represent 10% of the circle and sectors the remaining 90%. There are 128 gaps and 128 sectors around the circle. Since the gaps together ... one another. However, instead of allowing reads of any block from either disk, we keep the head of the first disk in the inner half of the cylinders, and the head of the second disk in the outer...

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Tài liệu Database Systems: The Complete Book- P7 doc

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... On the other hand, the key 23, which used to separate the first and second children of the second child of the root now represents the smallest key accessible from the second child of the ... addresses and enter them into the translation table if they are not already there. These pointers include both the pointers from records in the block to elseivhere and the addresses of the block itself ... ~ve follo~v the procedure for lookup of the record. and Tve place the new record in that bucket. If there is room in the block for the bucket then there is nothing more to do. The problem...

Tài liệu Database Systems: The Complete Book- P8 pptx

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... involve reading the data only once from disk. These are the one-pass algorithms. and they are the topic of this section. Lsually. they work only ~vherl at least one of the arguments of the operation ... Whether the set version or the bag version is wanted, the algorithms are es- sentially the same as that of Section 15.4.3, except that the way we handle the copies of a tuple t at the ... really are only two loops if ~ve look at the code at the right level of abstraction. The first, or outer loop, runs through the tuples of S. The other two loops run through the tuples of...

Tài liệu Database Systems: The Complete Book- P9 doc

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... which allows the database to surrive not only temporary system failures. but situations where the entire database is lost. Then, \ve must rely on a recent copy of the database (the archive) ... in the absence of any copy the buffer back to disk, and to the query processor to execute the queries other transactions or system errors. and it starts with the database in a and other database ... shows the complete translation to relational algebra. .&bola the y, the StarsIn from the outer query is joined n-ith the result of the subquery. The selection from the subquery is then...

Tài liệu Database Systems: The Complete Book- P10 ppt

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... iii. The customer selects a seat for the flight; seat data for the flight is ill database element C. io. The system gets the custo~ner.~ credit-card number and appends the bill for the ... indicate the files that comprise the log. Then, to recover, we find the last record of the top file, go to the file indicated, and find the last record there. <CKBT>, and in fact the log ... represel~ts the real ti111e at 1\-11ich events occur. Dotted lines link the actual events to the tinles at which they theoretically occur - the tiniestamp of the rransaction that performs the event....