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Oracle Interview Questions and Answers

1
Difference between varchar and varchar2 data types?

Varchar can store upto 2000 bytes and varchar2 can store upto 4000 bytes. Varchar will occupy space for NULL values and Varchar2 will not occupy any space. Both are differed with respect to space.

2
What are various joins used while writing SUBQUERIES

Self join-Its a join foreign key of a table references the same table.

Outer Join-Its a join condition used where One can query all the rows of one of the tables in the join condition even though they don't satisfy the join condition.

Equi-join-Its a join condition that retrieves rows from one or more tables in which one or more columns in one table are equal to one or more columns in the second table.

3
What file types compose the physical structure of an Oracle database?

At least one data file, redo log file, and control file.

4
Explain: a.) Integrity Constraints

It can be called as a declarative way in order to define a business rule for a table's column

5
What are the components of physical database structure of Oracle database?

Oracle database is comprised of three types of files. One or more datafiles, two are more redo log files, and one or more control files.

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