Jan 14, 2015

Merge and Merge join transformation in SSIS


MERGE TRANSFORMATION 
Using Merge Transformation we can combines two sorted data-set into single data-set basically Merge Transformation used to combines rows from two sorted data flows into one sorted data flow.
Following tasks you may perform using Merge Transformation:
  1. Suppose we have scenario like, we need to merge data from a database table and excel means we want to merge data from two different data sources. For such type of scenario you can use Merge Transformation.
  2. If we want to merge data from two same structured table but exists two different servers.
  3. Sometime we get error due to data in a row, after correcting errors in the data we can re-merge rows easily.
See below explanations may help you to understand Merge Transformation:
I do evaluate here, you already know about data source, data conversion, data flow, task flow, control flow etc.
Note:  Before Merge transformation we need to sort the data using Sort Transformation.
After sorting data add data path to Merge Transformation, a dialog box will be open See below:

Now choose one option from Input, suppose we chose Merge Input 1 same as we add data path from second source.
Note: If Merge input 1 and Merge input 2 column name are same then no issue otherwise we have to map column, see below.


If we don’t want to add data from input you can ignore here, means we don’t want to add cAddress column from Merge Input 2 so we will select <ignore> same you can do with Merge Input 1.
See below full data flow of merge transformation.




MERGE JOIN TRANSFORMATION
Merge join transformation is the popular tool which is used by most of BI developers, The Merge Join Combine to sorted data into one output using the FULL, LEFT or INNER JOIN.
You can configure the Merge Join transformation in the following ways:
·         Specify the join is a FULL, LEFT, or INNER join.
·         Specify the columns the join uses.
·         Specify whether the transformation handles null values as equal to other nulls.
For example, you can use a LEFT join to join a table that includes customer information with a table that lists the phone of customer. The result is a table that lists all customers and their phone numbers.



The implementation is same as Merge transformation except need to select Join Type in Merge join transformation editor dialog box, see below:
Here we need to select option of Join Type and (Full, Left or Inner join), suppose we select option inner join then select map the column from two shorted data sources (in above pic. cId mapped to cust_Id because cId Primary ke in customers table and foreign key in custPhone table ).


To see the result, we can enable data viewer after sorting and Merge Join transformation.
Result will be look like below:

Customers data set after sorting.



 Customer- phone data set after sorting.

Merge join transformation output.