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Lesson 8 DECODE and NVL functions
Objective Modify query results using the DECODE and NVL functions.
The DECODE and NVL functions are really special. They can be used for date, number, and character datatypes. I have found these two functions to be great time-savers.
DECODE
Think of DECODE as a mini-IF-statement. It can compare the value in a column or expression to a list of values and substitute a different value for each item on the list. The basic syntax is:
DECODE(col1,case1,value1 [, case2, value2,...] , 
 defaultvalue) 
Add as many case and value pairs as you need. The final value is used when col1's value does not match any of the cases. The MouseOver below shows an example of DECODE.
Oracle Decode Example
You can also use DECODE to create columns of summarized data in a single query.
NVL
NVL is a simple function that replaces a null value with the specified value. It is useful when you want to perform arithmetic on columns that might contain null values. In these cases, a null value will cause the arithmetic to result in a null value. To avoid this, you can substitute zero for null value using the NVL function. Values that are anything other than null remain unchanged. The syntax is shown below.
NVL syntax
The next lesson concludes this module.
Decode Nvl Functions - Exercise
Click the Exercise link below to write a query using DECODE and NVL.
Decode Nvl Functions - Exercise