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Tip of the Day
Language: Java
Expertise: Intermediate
Apr 28, 2000

Create a Method Alias for a Sybase- or Oracle-Style Built-In Function with SQL-J

This example shows how to create a method, and then an alias for that method, to act like the Sybase-style SUBSTRING built-in function. (Note that you can also perform methods of java.lang.String on any string within SQL-J; simply select STRINGVALUE.substring(). This example just shows what to do in order to keep using your favorite syntax).

Make a class with a static method returning the requested substring to perform the function.
  
import java.sql.*;
public class MyBuiltIns
{
public static String substring(java.lang.String theString,
int start, int length)
{
if (theString.length() > start+length-1)
{
return theString.substring(start-1,start+length-1);
}
else
{
return theString.substring(start-1, theString.length());
}
}
Compile the file and make sure that the class is in the CLASSPATH environment variable. Add the method as an alias.
  
CREATE METHOD ALIAS substr FOR MyBuiltIns.substring 
Enter SQL like:
  
SELECT substr(name, 1, 5) FROM customers
This is the same as:
  
SELECT name.substring(0,4) FROM customers 
Manoj K.
 
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