Some systems use a single currency as a base, which is something that I noticed recently when working with IBM Cognos Controller, e.g. USD to convert local currencies into. But what if you want / need to rebase into another currency but still retain the original base?
This doesn’t appear to be easy to achieve within Cognos Controller itself, but it is achievable within SQL and a wider SSIS framework.
The basis for rebasing exchange rates uses the technique of triangulation arbitrage. The technique is most often used within the banking system and more information can be found here: http://en.wikipedia.org/wiki/Triangular_arbitrage In principle you deal with two known exchange rates and one unknown.
For example, if you have an exchange rate base of USD and know that the GBP/USD exchange rate is 1.54631 and the EUR/USD exchange rate is 1.11470 and wish to rebase from USD to EUR. You would begin by finding the inverse rates of GBP/USD (1/1.54631 = 0.6467), multiply by the EUR/USD rate (0.6467*1.11470 = 0.72087649) which produces the EUR/GBP and then find the inverse (1/0.72087649 = 1.3872) to produce the GBP/EUR rate. In order to find the USD/EUR exchange rate one simply finds the reverse of the EUR/USD rate (1/1.11470 = 0.8971).
That might sound simple, but most exchange rates are held in a table across a range of dates. This complicates the calculation somewhat. I’ve used CTEs because I find that it makes the script neater and easier to debug. Below is an example of the triangulation using the Sales.CurrencyRate table in the AdventureWorks2012 database.
USE AdventureWorks2012
;
WITH
LocalExchange AS (
SELECT
ToCurrencyCode AS CurrencyCode
,CASE WHEN ToCurrencyCode <> ‘EUR’ THEN (1 / AverageRate) END AS LocalCurrencyConversion
,CurrencyRateDate
FROM [Sales].[CurrencyRate]
),
EuroExchange AS (
SELECT
ToCurrencyCode AS CurrencyCode
,CASE WHEN(ToCurrencyCode = ‘EUR’)THEN AverageRate END AS EuroConversion
,CurrencyRateDate
FROM [Sales].[CurrencyRate]
WHERE CASE
WHEN(ToCurrencyCode = ‘EUR’) THEN AverageRate END IS NOT NULL
)
SELECT DISTINCT
–Keys
C.CurrencyRateID
,C.CurrencyRateDate
,CASE
WHEN C.ToCurrencyCode = ‘EUR’ THEN ‘USD’
WHEN C.AverageRate = 1 THEN ‘EUR’
ELSE C.ToCurrencyCode
END AS CurrencyCode
,1/(CASE
WHEN C.AverageRate = 1 THEN 1 ELSE
(1 / (CASE
WHEN C.ToCurrencyCode <> ‘EUR’ THEN (L.LocalCurrencyConversion * E.EuroConversion)
ELSE C.AverageRate
END))
END) AS ImplicitEuroExchangeRate
–Measures
–,C.ExchangeRate AS ExchangeRate
FROM
[Sales].[CurrencyRate] AS C
INNER JOIN LocalExchange AS L
ON L.CurrencyRateDate = C.CurrencyRateDate
AND L.CurrencyCode = C.ToCurrencyCode
INNER JOIN EuroExchange AS E
ON E.CurrencyRateDate = C.CurrencyRateDate
WHERE
CASE
WHEN c.ToCurrencyCode <> ‘EUR’ THEN (E.EuroConversion * L.LocalCurrencyConversion)
ELSE 1
END IS NOT NULL
ORDER BY C.CurrencyRateID
As always, if you have any feedback and can suggest a simpler way of performing the triangulation I would love to hear it.
Meet the Team – Catherine Sachdev, Marketing Assistant
Next up we’re introducing you to Catherine Sachdev. Catherine joined us just over a year
Jan
Data Lineage with Azure Purview
I wrote an introductory Purview blog post previously, where I explored what the tool is
Jan
The Next Era of Retail: How Technology is driving change in a COVID-19 World
The retail sector is of great importance and accounts for almost 5% of GDP and
Jan
Meet the Team – Alex Kordbacheh, Junior Consultant
It’s time for another Meet the Team blog! This time we’re introducing you to Alex
Dec
Use cases for Recursive CTEs
Introductions Recursive CTEs are a way to reference a query over and over again, until
Dec
Azure Sentinel is named a ‘Leader’ in the Forrester Research Wave Report
Microsoft have recently announced that they have been named a Leader by Forrester Research in
Dec
Getting Started with Azure Purview
Azure Purview (a.k.a Data Catalog gen 2) has been released into preview and is currently
2 Comments
Dec
An Introduction to ApexSQL Complete – Integration with SSMS
We all know that the idea of add-ins is to make our lives easier. In
Dec