exp_011.htm

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<p><b><span style="font-size:22pt">Explaination 011: &nbsp;</span></b></p>

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	<p>
	This SELECT statement provides correct usage of NVL function to calculate columns for all employees. Oracle give you possibility to substitute a value in place of NULL. The basic syntax for NVL() is NVL(column_name, value_if_null). Notice that the column specified in NVL() contains an actual value. That value is what Oracle returns; when the column is NULL, the special string isreturned. The value specified to be returned if the column value is NULL must be the same datatype as the column specified. <br>
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	<p>
	  Incorrect Answers <br>
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	<p>
	  A: This SELECT statement will return NULL value for rows with NULL COMMISION_PCT column. <br>
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	<p>
	  B: There is no IFNULL() function in Oracle. <br>
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	<p>
	  C: The NVL2() function requires 3 parameters, not 2. Function NVL2(expr1, expr2, expr3) returns expr2 if expr1 is not NULL. If expr1 is NULL, it returns expr3. <br>
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	<p>
	  OCP Introduction to Oracle 9i: SQL Exam Guide, Jason Couchman, p. 31-32 <br>
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	<p>
	  Chapter 1: Overview of Oracle Databases
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