Database - Interview Questions and Answers for 'Igate' | Search Interview Question

Database - Interview Questions and Answers for 'Igate' - 4 question(s) found - Order By Newest

Frequently asked in Cognizant ( Based on 2 feedback )

Q1. What are Inner , Outer , Left and Right Joins in SQL ?

Ans. Inner join is the intersection of two tables on the condition defined by the where clause i.e will get records from both tables matched by a column.

Outer join is the union of two tables i.e will get all records from both tables and will put null in the columns where related records are not present.

Left Outer join is the left union of two tables i.e all records from the table on the left and values from the right table for related records else null for the columns from right table.

Right Outer join is the right union of two tables i.e all records from the table on the right and values from the left table for related records else null for the columns from left table.

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Q2. What is a self Join and give an example of a self Join ?

or

What is self Join and What is it's purpose ?

Database

Ans. When a Table Join itself , it's a Self Join. For example - we like to know the pair of department names where first dept has lesser employees than the later.

Select D1.name , D2.name from Dept D1, Dept D2 where D1.employee_count < D2.employee_count

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Q3. What is database Normalization ?

Database

Ans. https://en.wikipedia.org/wiki/Database_normalization

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Q4. What is connection pooling?

Database

Ans. It's a technique to allow multiple clients to make use of a cached set of shared and reusable connection objects providing access to a database or other resource.

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