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Interview Questions
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Database concepts Interview questions -
Part 4
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Question - Define aggregate and scalar functions.
Answer
Aggregate Functions return a single value by
operating against a group of values.
Scalar functions operate against a
single value.
Question - What are the restrictions applicable while creating
views?
Answer
Views can
be created referencing tables and views only in the current
database.
A view name must not be the same as any table owned by
that user.
You can build views on other views and on procedures
that reference views.
Rules or DEFAULT definitions can't be
associated with views.
Only INSTEAD OF triggers can be associated
with views.
The query that defines the view cannot include the
ORDER BY, COMPUTE, or COMPUTE BY clauses or the INTO keyword.
You
cannot define full-text index definitions for views.
You cannot
create temporary views
You
cannot create views on temporary tables.
Question - What is "correlated subqueries"?
Answer
In "correlated subqueries",
the result of outer query is passed to the subquery and the subquery
runs for each row.
Question - What is Data Warehousing?
Answer
Data
Warehousing is a process of storing and accessing data from central
location for some strategic decision. Data Warehouse is a collection
of subject oriented databases that
are design to support decision support functions.
Question - What is a join and explain different types of joins.
Answer
Joins are
used in queries to explain how different tables are
related.
Joins also let you select data from a table depending
upon data from another table.
Types of joins: INNER JOINs, OUTER
JOINs, CROSS JOINs.
OUTER JOINs are further classified as LEFT OUTER JOINS, RIGHT OUTER
JOINS and FULL OUTER JOINS.
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