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Dirty Reads: T10 reads a value which is updated by T9. This update has not been committed and T9 aborts.
T9
T10
Value of x old value =
200
UPDATE X
500
READ X
ROLLBACK
?
Here T10 reads a value that is updated by transaction T9 that has been aborted. Therefore T10 has read a value that would never exist in the database and hence the trouble. Here the difficulty is primarily of isolation of transaction.
why we fregment at all?
Draw an Entity-Relationship model for the relational schema given in the Appendix. Show all the entities, relationships, relationship names, and attributes and also underline the
various techniques of hashing?
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Create an entity relationship diagram, Database Management System
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Extend your CREATE TABLE statement from problem 3 with referential integrity constraints. Updates and deletes on related rows are restricted. 6. From examination of the sample data
multidimensional data model
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