PARAMETER MAPPING:
- Parameter file is used to store variables that can be used anywhere within the repository and can be used by any other mappings in the same repository.
- Parameter file can be used to store dates, characters, strings, and numbers.
- Parameter file is created by developing a mapping and the storing the target data in a file providing the correct output file Directory and the file name in the mapping.
- You can use the file by calling the file using correct path and file name in Properties Tab under Parameter File name.
(E.g.) In case of incremental load, for any table we can store max of date in the parameter file. - While loading the data in the target table we can compare the source data with the date in parameter file and load the new set of data from source to target.
How to create a Parameter Mapping?
- For storing Date in the parameter file, create a mapping with a dummy table having parameter variable name (Parameter) and target table.
- If processing the data not available in the target we can take the maximum of date in target table.
- Load the parameter value in the parameter target file and also mention the date format.
- While creating the session use the mapping and then put the correct directory path and file name.
- While using the same file for loading the data, the file can be used using the correct file name and directory path.
Records from BSE table can be extracted to BSE_TBL by following the same steps of extraction from NSE table to NSE_TBL using the parameter mapping.
Loading of records from BSE_TBL and NSE_TBL to STOCK_TRADING_FCT:
- Open the mapping designer and select the ‘Create Mapping’ in the ‘mapping’ option in the menu
- Give in the mapping name as m_Stock_trading as per the naming convention – DW loading
- From the navigator drag the two sources NSE_TBL and BSE_TBL.
- These two sources would be displayed along with the Source qualifier, which is read only.
- This source qualifier can created automatically i.e. whenever source is been dragged into the mapping designer source qualifier would be created automatically or else source qualifier can be created manually.
- Similarly target (STOCK_TRADING_FCT) can be dragged into the mapping designer.
- In the source qualifier the SQL query can be included in order to filter out the records from the sources. In our case we can pull in all the columns from both the source tables.
- Create an expression transformation in the mapping after the source qualifier and link all the columns from the source qualifier to the expression transformation.
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