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What is difference between SUBSTR and INSTR?

INSTR function search string for sub-string and returns an integer indicating the position of the character in string that is the first character of this occurrence. SUBSTR function return a portion of string, beginning at character position, substring_length characters long. SUBSTR calculates lengths using characters as defined by the input character set.

Which data type is used for storing graphics and images?

Raw, Long Raw, and BLOB.

What is difference between SQL and SQL*PLUS?

SQL is the query language to manipulate the data from the database. SQL*PLUS is the tool that lets to use SQL to fetch and display the data.

What is difference between UNIQUE and PRIMARY KEY constraints?

An UNIQUE key can have NULL whereas PRIMARY key is always not NOT NULL. Both bears unique values.

What is difference between Rename and Alias?

Rename is actually changing the name of an object whereas Alias is giving another name (additional name) to an existing object.

Rename is a permanent name given to a table or column whereas Alias is a temporary name given to a table or column which do not exist once the SQL statement is executed.

What are various joins used while writing SUBQUERIES?

=, , IN, NOT IN, IN ANY, IN ALL, EXISTS, NOT EXISTS.

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