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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.
The following data are required to be stored by a family physician. Family#, FamilyAddress, Patient#, PatientName, ServiceCode, ServiceFee, ServiceDate A family can have seve
The PROJECT operation The project operation is used to choose the records with specified attributes as discarding the others based on some related criteria. This is denotes as ∏
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Which operator is Cartesian product in relational algebra? Cartesian product in relational algebra is a binary operator. (It requires two operands. e.g., P X Q)
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