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91. What Is ROWID?
Date Posted: 07/03/2012
Ans: ROWID is a pseudo column attached to each row of a table. It is 18 characters long, block no, row number are the components of ROWID.
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92. Explain UNION, MINUS, UNION ALL And INTERSECT?
Date Posted: 07/03/2012
Ans: INTERSECT – returns all distinct rows selected by both queries. MINUS – returns all distinct rows selected by the first query but not by the second. UNION – returns all distinct rows selected by either query UNION ALL – returns all rows selected by either query, including all duplicates.
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93. Difference Between SUBSTR And INSTR?
Date Posted: 07/03/2012
Ans: INSTR (String1, String2 (n, (m)),
INSTR returns the position of the m-th occurrence of the string 2 in string1. The search begins from nth position of string1.
SUBSTR (String1 n, m)
SUBSTR returns a character string of size m in string1, starting from n-th position of string1
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94. Explain CONNECT BY PRIOR?
Date Posted: 07/03/2012
Ans: Retrieves rows in hierarchical order Eg. Select empno, ename from EMP where.
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95. What Is Correlated Sub-query?
Date Posted: 07/03/2012
Ans: Correlated sub-query is a sub-query, which has reference to the main query.
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96. What Is The Sub-query?
Date Posted: 07/03/2012
Ans: Sub-query is a query whose return values are used in filtering conditions of the main query.
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97. What Is Difference Between TRUNCATE & DELETE?
Date Posted: 07/03/2012
Ans: TRUNCATE commits after deleting entire table i.e., cannot be rolled back. Database triggers do not fire on TRUNCATE
DELETE allows the filtered deletion. Deleted records can be rolled back or committed. Database triggers fire on DELETE.
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98. What’s An SQL Injection?
Date Posted: 07/03/2012
Ans: SQL injection is when from data contains an SQL escape sequence and injects a new SQL query to be run.
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99. What Is The Parameter Substitution Symbol Used With INSERT INTO Command?
Date Posted: 07/03/2012
Ans: &
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100. What Is The Output Of The Following Query SELECT TRUNC(1234.5678,-2) FROM DUAL;?
Date Posted: 07/03/2012
Ans: 1200
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