Answer Posted / kiran chandra sarkar

PRIMARY KEY: A table can contain only one PRIMARY KEY. It
doesn’t allow null values; it is used as Foreign Key in
another Table (like Reference Key).

UNIQUE KEY: A Table may contain one or more UNIQUE
constraints. It’s allowing only one null value. Use this
key we maintain unique vales in the table.

FOREIGN KEY: A key used in one table to represent the value
of a primary key in a related table. While primary keys
must contain unique values, foreign keys may have
duplicates. For instance, if we use student ID as the
primary key in a Students table (each student has a unique
ID), we could use student ID as a foreign key in a Courses
table: as each student may do more than one course, the
student ID field in the Courses table (often shortened to
Courses. student ID) Will hold duplicate values.

What are the validations performed on the source data? If there are junk data available in the source data, how to eliminate it?

2080

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Explain database partitioning.

1124

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1101

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A design problem was given in which I was supposed to make a design for the data base for a given problem.

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1219

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How default key is different from primary key?

1080

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2268

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