SQL Server UK PostCode Distance Calculator

A tool for calculating the distance between two UK Post distances and finding a list of all post codes within a certain number of kilometers.

Click below to watch the walkthrough video:

Finding all Postcodes within X kilometers

To find a list of postcodes within X kilometers, use the Table Function postCodesWithinXkm. For example, to find all Postcodes with 5 kilometers of SW1A 0AA, you can use the below code.

SELECT * FROM postCodesWithinXkm('SW1A 0AA',5)

Calculating the distance between two Postcodes

To determine the distance between two postcodes, use the Scalar function distanceBetweenPostCodes. For Example: to find the distance between SW1A 0AA and SE10 0DX, you can use the below code.

SELECT dbo.distanceBetweenPostCodes('SW1A 0AA','SE10 0DX')

Returning a table with distance from one post to all Others

To find a list of all post codes and their distance to particular post, use the table function distanceToAllPostCodes

SELECT * FROM dbo.distanceToAllPostCodes('SW1A 0AA') a

Use Cases

Supose we have a CRM database containing a Prospects table containing a list of prospective client addresses and a Branch table containing all the addresses of our branches.

Using postCodesWithinXkm

If we a particular Branch was running a prompotion and we want to notify all Prospective clients within 5 km of the branch, we could use the below code to obtain a list of all the Prospective clients we should contact.

SELECT      a.ProspectName, a.ProspectEmail, a.PostCode
FROM        CRM..Prospects a
INNER JOIN  postCodesWithinXkm('PO19 1EL',5) b on a.PostCode = b.PostCode

The output would like something like:

ProspectName	ProspectEmail	PostCode
Acme Corp Ltd	jo@acme.co.uk	PO18 0AE
Tools4u Ltd	Ned@tools4u.com	PO20 2GU
Hal's meats	hal@halsmeats.co.uk	PO19 7EY

Using distanceBetweenPostCodes

We could use the code below to determine the number of Prospects within 5 km of each of our branches.

SELECT      a.PostCode As BranchPostcode, a.BranchName, count(b.Id) As CustomerCount
FROM        CRM..Branches a
INNER JOIN  CRM..Prospects b 
ON PostCodeDistanceCalculator.dbo.distanceBetweenPostCodes(a.PostCode,b.PostCode)<5
GROUP BY    a.PostCode

The output would like something like:

Branch Postcode	Branch	Customers
BN1 2RE	Brighton	15
PO19 1EL	Chicester	37
W4 5TA	Chiswick	89

Using distanceToAllPostCodes

Suppose we wanted to determine the closest Branch for each Prospective Client. We can make use of distanceToAllPostCodes to determine the distance of each branch to each Prospective client and order by the closet.

SELECT  a.ProspectName, c.BranchName, b.distance, 
        ROW_NUMBER() OVER (PARTITION BY a.ProspectName ORDER BY b.distance ) As DistanceRank
FROM        CRM..Prospects a
CROSS APPLY PostCodeDistanceCalculator.dbo.distanceToAllPostCodes(a.PostCode) b
INNER JOIN  CRM..Branches c on b.Postcode = c.Postcode

The output would like something like:

ProspectName	BranchName	Distance
Acme Corp Ltd	Brighton	7.477788367078679
Acme Corp Ltd	Chicester	82.13621491096778
Acme Corp Ltd	Chiswick	86.65279491895977

How to deploy the database to your local SQL Server instance

1. Clone the repo
2. Open the Solution in Visual Studio
3. Open PopPostCodes.sql and edit the file location 'C:\Users\timga\source\repos\PostCodeDistanceCalculator\PostCodeDistanceCalculator\Files\ukpostcodes.csv' to point to the correct location.
4. Open the PostCodeDistanceCalculator.publish.xml and select the target Instance and database to deploy to.

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Contains Ordnance Survey data © Crown copyright and database right 2021

Contains Royal Mail data © Royal Mail copyright and database right 2021

Source: Office for National Statistics licensed under the Open Government Licence v.3.0