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How to perform join between data flow/data set in SSIS

Lookup transformation is responsible for joining columns to the data flow/data set, by accessing additional information in a related table based on values in common columns.

Problem: We have a table EMP which data are fetching by OLEDB Source, this table contains column FName, LName, Salary, and Country. In the flow, we need to add column empAddress and empPhone of Employees which information are in EMPDETAILS table.

Solution: We would use the Lookup Transformation. Now see below the use of lookup transformation.


Create table EMP(
Id int identity(1,1),
FName VARCHAR(50),
LName VARCHAR(50),
Salary DECIMAL(18,2),
Country VARCHAR(50)
)
insert into EMP (FName,LName,Salary,Country)
Values('Dilip','Singh',20000,'IND')
insert into EMP (FName,LName,Salary,Country)
Values('Viru','Verma',40000,'USA')
insert into EMP (FName,LName,Salary,Country)
Values('Anil','Singh',30000,'UK')
insert into EMP (FName,LName,Salary,Country)
Values('Raju','Shukla',25000,'IND')
insert into EMP (FName,LName,Salary,Country)
Values('Raj','Kushwaha',20000,'AUS')
insert into EMP (FName,LName,Salary,Country)
Values('Salim','Sekh',26000,'PAK')
insert into EMP (FName,LName,Salary,Country)
Values('Nirmit','Katihar',27000,'AUS')
insert into EMP (FName,LName,Salary,Country)
Values('Dilip','Singh',23000,'AUS')
select * from EMP

Create Table EMPDETAILS
(
Id int identity(1,2),
empId int not null,
empAddress varchar(200),
empPhone Varchar(20)
)
Insert into EMPDETAILS(empId,empAddress,empPhone)
Values (1,'Delhi','9015518898')
Insert into EMPDETAILS(empId,empAddress,empPhone)
Values (2,'california','8898283856')
Insert into EMPDETAILS(empId,empAddress,empPhone)
Values (3,'Bristol','8898283226')
Insert into EMPDETAILS(empId,empAddress,empPhone)
Values (4,'Haryana','9073348898')
Insert into EMPDETAILS(empId,empAddress,empPhone)
Values (5,'Kingston','8875647643')
Insert into EMPDETAILS(empId,empAddress,empPhone)
Values (6,'Lahor','8876664646')
Insert into EMPDETAILS(empId,empAddress,empPhone)
Values (7,'Lahor','8876664646')
Insert into EMPDETAILS(empId,empAddress,empPhone)
Values (18,'UP','9087765564')



First, drag and drop an OLEDB Source and make connection manager then select EMP table (I hope you know about OLEDB Source). In the dataset, you will find only columns like FName, LName, Salary, Country now we have required additional information like Address and Phone which belongs to EMPDETAILS table. 
  
Now we will use Lookup Transformation to add or join column from EMPDETAILS table based on common column, In EMPDETAILS table empId is the foreign key of EMP it means empId is common between EMP and EMPDETAILS on this basis we can perform Lookup Transformation.

Drag and drop Lookup Transformation and add flow path from Oledb Source and edit it. It will look like below.

Here I will stop the example and start the explain about lookup. 

GENERAL


Full cache: Full Cache is responsible for generating and loading the reference dataset into cache before the Lookup transformation is executed.

Partial cache: Partial Cache is responsible for generating the reference dataset during the execution of the Lookup transformation. Load the rows with matching entries in the reference dataset and the rows with no matching entries in the dataset into the cache.

No cache: No-cache is responsible for generating the reference dataset during the execution of the Lookup transformation. No data is loaded into cache.

Cache connection manager: Cache connection manager is responsible for configuring the Lookup transformation to use a Cache connection manager. This option is available only if the Full cache option is selected.
OLE DB connection manager: OLEDB the connection manager is responsible for configuring the Lookup transformation to use an OLE DB connection manager.

Specify how to handle rows with no matching entries

Select an option for handling rows that do not match at least one entry in the reference data set.

When you select Redirect rows to no match output, the rows are redirected to a no-match output and are not handled as errors. The Error option on the Error Output page of the Lookup Transformation Editor dialog box is not available.

When you select any other option in the Specify how to handle rows with no matching entries list box, the rows are treated as errors. The Error option on the Error Output page is available.

CONNECTION


OLE DB connection manager: Here you can select an existing OLE DB connection manager from the list, or create a new connection by clicking New.

Use a table or view: Here you can select a table from the list, or you can create a new table or view on by clicking New.

Use Result of an SQL Query: By choosing this option, you can browse to a pre-existing query, build a new query check query syntax and preview query result.


Build Query: Create the Transact-SQL statement to run by using Query Builder, a graphical tool that is used to create queries by browsing through data. It looks like below.

   
Browse Query: Using this option, you can browse a pre-existing query.

Parse Query: This is responsible for checking the syntax of the query

Preview: This is responsible to preview query result.


COLUMNS

Available Inputs Column: These columns come through data flow from a connection source. The input columns and the lookup column must have matching data types. Use a drag-and-drop operation to map available input columns to lookup columns. You can also map input columns to lookup columns using the keyboard, by highlighting a column in the Available Input Columns table, pressing the Application key, and then clicking Edit Mappings.

Available Lookup Columns: The lookup columns are those columns comes through a reference table in which you want to look up values that match the input column. Use a drag-and-drop the operation to map available input columns to lookup columns. Use the checkboxes to select lookup columns in the referenced table on which to perform the lookup operations.

Lookup Column: These columns comes when you select a column from available lookup columns. The selections are reflected in the checkbox selections in the Available Lookup Columns table.

Lookup Operation:  Select the option to perform an operation on the lookup column.

Output Alias: The selections are reflected in the checkbox selections in the Available Lookup Columns table.


ADVANCED


Note: This option available only for Partial and no-cache.

Cache size (32-bit):  Adjust the cache size (in megabytes) for 32-bit computers. The default value is 5 megabytes.

Cache size (64-bit):  Adjust the cache size (in megabytes) for 64-bit computers. The default value is 5 megabytes.

Enable cache for rows with no matching entries:  Cache rows with no matching entries in the reference dataset.

Allocation from cache: Specify the percentage of the cache to allocate for rows with no matching entries in the reference dataset.
Modify the SQL statement:  Modify the SQL statement that is used to generate the reference dataset.

Error and Output: I will explain it later in Error Handling...

Now I am starting output explanation...


Please apply Data viewers on every path, input data looks like below.

Here only on column match with a column in the referenced table. For example, the id of EMP(input table) is matched with empId in EMPDETAILS(reference table).


Here show matched output data, you can see empAddress and empPhone columns are joined in the dataset.


like this, you can see not matched data as given below.