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Looping using Expression Transformation in Informatica

One of the most common used transformation in Informatica is Expression transformation. In Expression transformation we can perform various operations such as data conversions i.e to_date,to_char, string manipulation such as substr,instr etc. Now coming to one of the widely and prominent task which we perform using Expression transformation is looping a value.

Expression transformation has three types of ports i.e. input,variable and output.Only output port values can be propagated to next transformations. So in order to pass values of input and variable ports to next level of transformation these must be assigned to output ports.The order of execution in Expression transformation is top to bottom and first input then variable and finally output ports are processed.

let us consider the following scenario
 
The files should be generated with employee name as file name and that particular file should have the details of that respective employee only, if the employee has more than one record then both the records should be pulled into the file


Data passing through the flow is as follows



When the first record passes through the expression the data will be in following way



The values are parsed in the following order input,variable and output from top to bottom

When the second record passes the resultant flow will be in following way


As we can see we are using variable port for comparison of values.We will use O_Flag for generating files by using transaction control transformation



Hope this article helps you in understanding flow of data in Expression transformation

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