- As the name says that (SCD) Slowly Changing Dimensions have something to do with the dimensions. Now there are some data which are not frequently changing like master data for e.g. Country Master, Currency Master, etc. So now to make changes in those data we use SCD (Slowly Changing Dimensions).
- Now in slowly changing dimensions there are some options where if the data is duplicate and is changing what action should be taken, either keep the previous data along with the new data or overwrite the new data with the previous data.
- Those 3 options are, Fixed Attribute, Changing Attribute, and Historical Attribute.
- In Fixed Attribute any changes made to the column are treated as errors, in Changing attribute the changes made to the column are overwritten on the old data in column, and in Historical attribute the old data and the new data both are kept.
- SCD should be used when we have very few records to be changed. It is not used for bulk and frequent record changes.
SCD is one such important part of SSIS which has fundamental that need to be explained before starting SCD practical’s.
Type 1 & Type 2:
- Type 1 is known as changing attribute where the changes made to the column over write the existing values.
- Type 2 is known as the Historical Attribute where changes made to the column are saved as new records and the previous records are marked as outdated.
- Now when we configure the SCD it automatically write the code where if the records are new it inserts them into the table and if they are modified then they are taken care of accordingly by using Type 1 & Type 2. The OLEDB command takes care of those records which are changed or modified or updated.
- Param’s are nothing but parameters used in an Update SQL query in OLEDB command. The sequence is more important because depending on it we have to do the mapping. So param_0 is the starting of the sequence. If the query has 3 parameters the sequence goes in this way param_0, param_1, param_2.
- Unicode characters are used if we want our data to be multi lingual. So we cannot use Non Unicode characters in our database or during BI because the data can be in one language or it can be multi lingual.
Many more such other SSIS topic concept gets covered practically during
MSBI offline training at Mumbai
