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Implement Slowly Changing Dimensions in ODI

Hello friends!
In this tutorial we will learn how to implement the concept of Slowly Changing Dimensions (SCD) using Oracle Data Integrator. As the name suggests, SCD in data warehousing refers to the slow change in data rather than the change on a regular basis. It is applicable in those cases where the attribute for a record varies over time.
There are three basic types of SCD’s:
1.Type 1 – Overwrite old values
In this case, new record replaces the original record. No copy of the original record exists.
2.Type 2 – Create a new record
In this case, a new record is added to the dimension table.
3.Type 3 – Create new fields
In this case, the latest update to the changed values can be seen. The original record is modified to reflect the change.
So now let’s begin implementing SCD using Oracle Data Integrator. Open ODI Studio and follow the below steps!
Pre-requisites: Oracle 10g Express Edition with *SQL Plus, Oracle Data Integrator 11g (version 11.1.1.7)
Step 1: Create source, target tables for SCD using *SQL Plus
Source table
create table scd_test(EmpId int, EmpName varchar2(30), DeptName varchar2(30), salary number(6,2));
Insert few rows of dummy data inside the source table.
insert into scd_test values(101,'Karan','Computer',2200.23);
insert into scd_test values(102,'Mahesh','Computer',3200.53);
insert into scd_test values(103,'Prasad','Mechanical',5300.13);
Target table
create table scd_target(EmpId int, EmpName varchar2(30), DeptName varchar2(30), salary number(6,2), joining_date date, flag number);
Step 2: Create models for source and target tables
Under Designer tab, create a new Model folder and then right click it, select Models–>Create new model. Reverse engineer both the source and the target tables under the same model. Provide any existing Oraclelogical schema while re-factoring.
creating data model
Step 3: Modify target table model and it’s columns for SCD
Open the target table datastore and change OLAP type to slowly changing dimension.
Then expand your target datastore to get all columns. Open required columns one by one and do the changes as follows!
snap_4
column_2
column_3
column_4
column_5
column_6
column_1
Step 4: Create new interface
While creating new interface select IKM as Oracle Slowly Changing Dimension. Map the source and the target tables. For columnsjoining_date and flag specify the implementation as shown below!
Creating interface
Creating interface
interface_snap_2
interface_snap_3
interface_snap_4
interface_snap_5
interface_snap_6
interface_snap_7
Run the interface without any errors. View the target table data.
output_1
snap_2
Running the interface for the first time
Running the interface for the first time
Now, update few records of the source table. In this case, I will update name and salary of employee. Hence as per SCD Types 1 and 3, first a new record will be inserted since we had selected Add row on change for Employee name and then salary will be overwritten as we had selectedOverwrite on change for Employee salary.
update scd_test set empname='nitesh' where empid=101;
update scd_test set salary=5634.43 where empid=102;
Run the interface again and then view the target table data. It now reflects SCD.
Output data
Output data
output_new_2
That completes this tutorial. Keep visiting for more!
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