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What is aggregate function? Briefly describe it?
Aggregate functions are functions that take a collection of values as input and return a one value. SQL offers 5 built-in aggregate functions:
a) Average: avg
b) Minimum:min
c) Maximum: max
d) Total:sum
e) Count:count
Average: avg
Select avg (balance)
From account
Where branch-name='perryridge'
Count :count
Select branch-name,count(distinct customer-name)
From depositior,account
Where depositor.account-number=account.account-number
groupby branch-name
Explain data abstraction? Data abstraction Data abstraction is a methodology in which enables us to isolate how a compound data object is utilized from the details of how it is
Define the Attribute Inheritance The attributes of a higher level entity set are inherited through a lower level entity set made by specialization-generalization hierarchy. Nam
let us consider a table having 2200 records and the fixed size of the table to be considered as 25.then how many numbers of table is requredto perform horizontal fragmentation
What is the difference between a key and a superkey? Key - A key a single attribute or a combination of two or more attributes of an entity set which is used to identify one
What is an E-R model? Draw an E-R Diagram for the company database with following Descriptions? The company is organized within departments. Each department has a unique name a
What does Aggregation mean?
Suppose R is a relation with attributes A1, A2,..., An. As a function of n, tell how many superkeys R has, if: 1.1 The only key is A1. 1.2 The only key is A1 and A2. 1.3 The o
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Soccer player ER Diagram to Relational database schema
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