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TechTip: SQL GetMiles Function

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SQL functions allow you to use complex calculations to define field values. A good example is the calculation used to determine the distance between two ZIP codes. This type of function can be extremely useful within Web-based applications for calculating freight costs or for displaying store locations closest to a defined ZIP code. This tip describes how to create an SQL function that you can use to determine the distance between two ZIP codes and how to use this function within applications.

ZIP It Up!

Before you can start examining the function that determines distance between two ZIP codes, you need to examine the data required. Included with the code for this article is zipfile.savf, a physical file containing five-digit United States ZIP codes, along with their associated state abbreviations and longitude and latitude values. This data is from the 2000 U.S. Census Bureau census. The DDS source for this file is in Figure 1.

A* ZIP CODE MASTER FILE                                           
A*                                                                
A* COMPILE USING:  CRTPF FILE(QGPL/ZIPCODES)                      
A*                       SRCFILE(QDDSSRC)                         
A*                                                                
A          R ZIPS                                                 
A            ZIPCD          5          TEXT('5 DIGIT ZIP')        
A            STAB           2          TEXT('STATE ABBREV')       
A            LONG          15  5       TEXT('LONGITUDE')          
A            LAT           15  5       TEXT('LATITUDE')           
A          K ZIPCD                                                
A          K LONG                                                 
A          K LAT                                                  

Figure 1: This is the DDS source for the ZipCodes physical file.

To load this file on your iSeries, you must first create the save file in QGPL using the following command:

CRTSAVF FILE(QGPL/ZIPSSAVF) TEXT('Zip Code Data Save File')

Once you've created the save file, you're ready to load the save file data into this file using FTP, as shown in Figure 2.

ftp> open 192.168.0.3
Connected to 192.168.0.3.
220-QTCP at 192.168.0.3.
220 Connection will close if idle more than 15 minutes.
User (192.168.0.3:(none)): userid
331 Enter password.
Password:
230 USERID logged on.
ftp> cd QGPL
250 "QGPL" is current library.
ftp> bin
200 Representation type is binary IMAGE.
ftp> put zipdata.savf zipssavf
200 PORT subcommand request successful.
150 Sending file to member ZIPSSAVF in file ZIPSSAVF in library QGPL.
250 File transfer completed successfully.
ftp: 3020160 bytes sent in 3.56Seconds 847.65Kbytes/sec.
ftp> quit                         

Figure 2: Load the ZIP code data file onto the iSeries using FTP.

Within this example, replace the IP address shown (192.168.0.3) with the IP address of your iSeries.

Next, you'll have to restore the physical file with the RSTOBJ command:

RSTOBJ OBJ(ZIPCODES) SAVLIB(QGPL) DEV(*SAVF) OBJTYPE(*FILE)
SAVF(QGPL/ZIPSSAVF)

Building the Function

Now that you have the ZIP code data loaded into your iSeries, you're ready to take a look at the SQL function that you'll use with this data. This function calculates the number of air miles, nautical miles, or kilometers between ZIP codes, using the longitude and latitude points associated with each ZIP code. The source for the GetMiles function is shown in Figure 3.

CREATE FUNCTION QGPL.GETMILES(@ORIGZIP VARCHAR(5),@DESTZIP VARCHAR(5), 
 @UNIT VARCHAR(1))
RETURNS DECIMAL(13,0)  
LANGUAGE SQL    
BEGIN           
      DECLARE @PI FLOAT;      
      DECLARE @X FLOAT;        
      DECLARE @DISTANCE FLOAT;  
      DECLARE @LAT1 FLOAT;           
      DECLARE @LAT2 FLOAT;  
      DECLARE @LONG1 FLOAT;        
      DECLARE @LONG2 FLOAT;   
                                                                        
      SELECT LAT, "LONG" INTO @LAT1, @LONG1  
      FROM QGPL.ZIPCODES WHERE ZIPCD = @ORIGZIP;  
      SELECT LAT, "LONG" INTO @LAT2, @LONG2         
      FROM QGPL.ZIPCODES WHERE ZIPCD = @DESTZIP;             
                                                               
      SET @PI=3.1415927;        
      SET @X = (SIN((@LAT1 * @PI/180)) * SIN((@LAT2* @PI/180)) 
               + COS((@LAT1* @PI/180)) * COS((@LAT2* @PI/180)) 
               * COS(ABS(((@LONG2* @PI/180))-((@LONG1*@PI/180))
      SET @X = ATAN((SQRT(1-(@X*@X)))/@X);   
      SET @DISTANCE = (1.852 * 60.0 * ((@X/@PI)*180));  
      IF (UPPER(@UNIT)='M') THEN       
           SET @DISTANCE = (@DISTANCE * .621371192);       
      ELSE           
           IF (UPPER(@UNIT)='N') THEN 
                SET @DISTANCE = (@DISTANCE * 0.539956803);     
           END IF;               
      END IF;         
      RETURN @DISTANCE;     
END

Figure 3: Use this source to create the GetMiles function.
To create this function, copy the source in Figure 3 into a source physical file (QSQLSRC, for example). Next, use the RUNSQLSTM command:

RUNSQLSTM SRCFILE(QGPL/QSQLSRC) SRCMBR(GETMILES)
COMMIT(*NONE) NAMING(*SQL)

The formula contained within the GetMiles function uses the circumference of the Earth along with the longitude and latitude values that correspond to each ZIP code supplied. The function accepts three parameters: the five-character origin ZIP, the five-character destination ZIP, and the one-character unit of measure value representing the value to be returned. The value calculated is represented as kilometers by default but is converted to either air miles or nautical miles, based on the third parameter. Use a value of 'M' for air miles or a value of 'N' for nautical miles. Any other value specified will return the resulting distance in kilometers.

Once the function has been created, you can test it using the Interactive SQL console by typing the command STRSQL. From the console, type this SELECT statement:

SELECT QGPL.GETMILES('18222', '90210', 'M')
FROM QSYS2.SYSCOLUMNS

When executed, this statement will return multiple rows showing the air miles distance between these two ZIP codes. In this example, the file specified on the FROM clause is used for example purposes only.

Putting the Function to Use

Once you've successfully built and tested the GetMiles function, you're ready to put it to practical use. The example shown below calculates a shipping charge based on the origin ZIP (ORGZIP) and destination ZIP (DSTZIP) fields from the ORDERS file and joins to the CARRIERS file to get the rate per mile (RTPRMI) value.

SELECT ORGZIP, DSTZIP, QGPL.GETMILES(ORGZIP, DSTZIP, 'M') AS DIST,
QGPL.GETMILES(ORGZIP, DSTZIP, 'M') * RTPRMI AS FRTCST
FROM ORDERS INNER JOIN CARRIERS ON ORDERS.CARR = CARRIERS.CARR

A slightly more complicated example uses the function as part of an ORDER BY clause to return the data based on distance in miles. The statement for this example is shown below.

SELECT STNAME, STADD1, STADD2, STCITY, STSTAT, STZIP,
QGPL.GETMILES('18222', STZIP, 'M')
FROM STORES
ORDER BY QGPL.GETMILES('18222', STZIP, 'M')

This is an example of how you would use the function to display locations closest to a defined location. For instance, you could use it to create Web pages that allow a user to display stores closest to their home (the specified origin ZIP). To achieve that, you would replace the origin ZIP in the example with the value of the variable containing the user's origin ZIP.

This example shows how you can take an otherwise difficult task and make it a simple part of an SQL statement. This function has oodles of uses, a few of which we've examined here, but many more of which you'll discover on your own now that you've got GetMiles.

Mike Faust is MIS Manager for The Lehigh Group in Macungie, Pennsylvania. Mike is also the author of the books The iSeries and AS/400 Programmer's Guide to Cool Things and Active Server Pages Primer from MC Press. You can contact Mike at This email address is being protected from spambots. You need JavaScript enabled to view it..

Mike Faust

Mike Faust is a senior consultant/analyst for Retail Technologies Corporation in Orlando, Florida. Mike is also the author of the books Active Server Pages Primer, The iSeries and AS/400 Programmer's Guide to Cool Things, JavaScript for the Business Developer, and SQL Built-in Functions and Stored Procedures. You can contact Mike at This email address is being protected from spambots. You need JavaScript enabled to view it..

MC Press books written by Mike Faust available now on the MC Press Bookstore.

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