how to do ddt in postman

-- Use collection runner and select external file csv , json 

		How does Postman know which column is used for which data in csv file ? 

		postman will look for variable with same name as column name 
		and set the value of the variable for that column name 

		for example : 
			if you have collection variable called zip 
			and you have column name for your csv file as zip 
			it will get the value from the zip column of csv file