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@praveenkumar-66Ze92 • Dec 21, 2011
Atomicity - An atom cannot be subdivided further. So should be the transaction.
Consider a bank transfer account. In that, A transfers 10 to B. So, database'ically',
Operation #1: 10 is subtracted from A.
Operation #2: 10 is added to B.
Atomicity is both these two operations should happen or none should happen. It cannot be only Operation #1 happened or Operation #2 happened. 😀 Both the operations happened is called a Transaction. 😀 -
@praveenkumar-66Ze92 • Dec 21, 2011
Aggregation: There are 7 functions in aggregation in databases. All these can be performed only on multiple rows / data.AVG() - Returns the average value COUNT() - Returns the number of rows FIRST() - Returns the first value LAST() - Returns the last value MAX() - Returns the largest value MIN() - Returns the smallest value SUM() - Returns the sum