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Lock Based Protocol
A lock is nothing but a mechanism that tells the DBMS whether a particular data item is being used by any transaction for read/write purpose. As there are two types of operations, i.e. read and write, whose basic nature are dissimilar, the locks for read and write operation might be behave differently.
Read operation performed by dissimilar transactions on the same data item poses less of a challenge. The value of the data item, if constant, can be read by any number of transactions at any given time.
(a) Why did SAP introduce the extended star schema?
What is a candidate key? Minimal super keys are known as candidate keys.
Create a view emp_dep containing e_name and number of dependents from the tables employee and dependent of (i) CREATE VIEW emp_dept AS SELECT ename, COUNT(*) FROM employee, dep
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what is Nested relational model? Explain with examples.
This assignment concerns the Research database. The database ER model is shown above, where attributes are omitted for clarity. The relational model for the database is: Departm
Why are cursors necessary in embedded SQL? A cursor is an object used to store the output of a query for row-by-row processing through the application programs. SQL statements
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Explain CNT in the respects of QBE ? CNT: It is one of the aggregation commands given in QBE. It is used to identify number of tuples
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