The join condition contains ports from both input sources that must match for the Integration Service to join two rows. Depending on the type of join selected, the Integration Service either adds the row to the result set or discards the row. The Joiner transformation produces result sets based on the join type, condition, and input data sources.
Before you define a join condition, verify that the master and detail sources are configured for optimal performance. During a session, the Integration Service compares each row of the master source against the detail source. To improve performance for an unsorted Joiner transformation, use the source with fewer rows as the master source. To improve performance for a sorted Joiner transformation, use the source with fewer duplicate key values as the master.
By default, when you add ports to a Joiner transformation, the ports from the first source pipeline display as detail sources. Adding the ports from the second source pipeline sets them as master sources. To change these settings, click the M column on the Ports tab for the ports you want to set as the master source. This sets ports from this source as master ports and ports from the other source as detail ports.
You define one or more conditions based on equality between the specified master and detail sources. For example, if two sources with tables called EMPLOYEE_AGE and EMPLOYEE_POSITION both contain employee ID numbers, the following condition matches rows with employees listed in both sources:
EMP_ID1 = EMP_ID2
Use one or more ports from the input sources of a Joiner transformation in the join condition. Additional ports increase the time necessary to join two sources. The order of the ports in the condition can impact the performance of the Joiner transformation. If you use multiple ports in the join condition, the Integration Service compares the ports in the order you specify.
The Designer validates datatypes in a condition. Both ports in a condition must have the same datatype. If you need to use two ports in the condition with non-matching datatypes, convert the datatypes so they match.
If you join Char and Varchar datatypes, the Integration Service counts any spaces that pad Char values as part of the string:
Char(40) = "abcd"
Varchar(40) = "abcd"
The Char value is “abcd” padded with 36 blank spaces, and the Integration Service does not join the two fields because the Char field contains trailing spaces.
The Joiner transformation does not match null values. For example, if both EMP_ID1 and EMP_ID2 contain a row with a null value, the Integration Service does not consider them a match and does not join the two rows. To join rows with null values, replace null input with default values, and then join on the default values.