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<p><b><span style="font-size:22pt">Explaination 069: &nbsp;</span></b></p>


	<p>
	<span style="font-size:18pt">Index will be useful if the indexed column contains a wide range of values. Especially B-tree 
	  indexes will work better for tables with a wide range of values. But for tables just with some distinct values bitmap indexes will be more helpful. <br>
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	  <span style="font-size:18pt">Incorrect Answers <br>
	</span></p>

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	  <span style="font-size:18pt">A: Oracle automatically creates index for NOT NULL columns, so you don't need create an index yourself. <br>
	</span></p>

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	  <span style="font-size:18pt">B: There are only table names in the FROM clause, not columns. <br>
	</span></p>

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	  <span style="font-size:18pt">C: Index may be will not work if the indexed columns are part of an expression. You need to avoid expressions if you want to use index. <br>
	</span></p>

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	  <span style="font-size:18pt">OCP Introduction to Oracle 9i: SQL Exam Guide, Jason Couchman, p. 322-331 <br>
	</span></p>

	<p>
	  <span style="font-size:18pt">Chapter 3: Creating Other Database Objects in Oracle
	</span></p>

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