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Sunday, October 18, 2020

How to handle Case statement in Azure Data Factory (ADF) compare to SSIS?

This post will describe how do you use CASE WHEN statement in Azure data factory(ADF). If you are coming from SSIS background, you know a piece of SQL statement will do the task. However let's see how you do it in SSIS and the very same thing can be achieved in ADF.

Problem statement:

For my simple scenario, In case PortfolioTypeCode is either 'Mutual Fund' or 'Pooled Fund' it should return 1 Else it should return 0.

 

How do you do in SSIS?

In SSIS, under data flow you will have OLEDB source like below fig 1:

Fig 1: SSIS OLEDB source

 

And open the OLEDB source and then Write SQL command like below and you are done:

SELECT Col1,

          CASE WHEN PortfolioCode IN('Mutual fund','Pooled fund')

            THEN 1

            ELSE 0

END  IsFund,

Col2

From Table1

Fig 2: CASE WHEN under SQL command in SSIS

 

How do you implement in ADF?

However in ADF, to achieve the same you need to use Expressions. ADF have very same concept of data flow like SSIS. In the data flow, after the source dataset is established you can add 'Derived Column' activity like below Fig 3:

Fig 3: Adding derive column under data flow

 

Now you can give a new column name and then add the expression (Fig 4):

Fig 4: Derived column expression

 

Let's see how Case expression works: it takes 3 arguments, those are condition, true and false. However, it can have alternating condition which describe in the figure 5:

Fig 5: Case in Expression

 

For my simple scenario, If PortfolioTypeCode is either 'Mutual Fund' or 'Pooled Fund' it should return 1 Else it should return 0.

Since you can't have CASE WHEN rather using case as Expression, the code will look like below:

  case( PortfolioTypeCode=='Mutual Fund',1,

       PortfolioTypeCode=='Pooled Fund',1,0)

 

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