# Sample transformation walkthrough using the Lookup field

The following example transformation demonstrates how to use the **Lookup** field. The transformation processes a CSV file and feeds its data into the Avro Input step. The Avro Input step decodes the Avro structure using a lookup field consisting of an **atm\_id** variable mapped to an *atm* field.

1. Save the following code block in a text file as `atm.schema`.

   ```
   {
     "type": "map",
           "values":{
           "type": "record",
           "name":"ATM",
           "fields": [
                     {"name": "serial_no", "type": "string"},
                     {"name": "location", "type": "string"}
           ]
           }
   }
   ```
2. Save the following code block in a text file as `simpleexample.csv`:

   ```
   atm|atms
   atm1|{"atm1": {"serial_no": "zxy555", "location": "Uptown"}, "atm2": {"serial_no": "vvv242", "location": "Downtown"}, "atm4": {"serial_no": "zzz111", "location": "Central"}, "atm6": {"serial_no": "piu786", "location": "Eastside"}, "atm10": {"serial_no": "hbc999", "location": "Westside"}, "atm20": {"serial_no": "mmm456", "location": "Lunar city"}}
   atm2|{"atm1": {"serial_no": "zxy555", "location": "Uptown"}, "atm2": {"serial_no": "vvv242", "location": "Downtown"}, "atm4": {"serial_no": "zzz111", "location": "Central"}, "atm6": {"serial_no": "piu786", "location": "Eastside"}, "atm10": {"serial_no": "hbc999", "location": "Westside"}, "atm20": {"serial_no": "mmm456", "location": "Lunar city"}}
   atm4|{"atm1": {"serial_no": "zxy555", "location": "Uptown"}, "atm2": {"serial_no": "vvv242", "location": "Downtown"}, "atm4": {"serial_no": "zzz111", "location": "Central"}, "atm6": {"serial_no": "piu786", "location": "Eastside"}, "atm10": {"serial_no": "hbc999", "location": "Westside"}, "atm20": {"serial_no": "mmm456", "location": "Lunar city"}}
   ```
3. Create a transformation with a CSV File Input step and a hop from the CSV Input step to the Avro Input step.

   ![Avro Input Sample CSV Transform](/files/e7FDbbMEpkRKzqrqEm1Y)
4. Configure the CSV File Input step as shown below, where the file name is the path to the `simpleexample.csv` file on your system:

   ![Avro Input Sample CSV File Input](/files/BCM3w8YvVSUfyJiDnnrI)

   **Note:** Make sure that the delimiter is the pipe character.
5. Configure the Avro File Input step tabs as shown below, where the schema is the path to the `atm.schema` file on your system:

   ![Avro Input Sample Source Config](/files/DNjXEYqb2hT3X3ZjuTRO)
6. Click **Get fields** to populate the **Avro fields** table. Enter the **Indexed values**field as shown below:

   ![Avro Input Sample Avro Fields Config](/files/n9FgNpPFEiIxsHsWdVP5)

   **Note:** Make sure to select the **Pass through fields from previous step** option.
7. Enter the following values in the **Lookup fields** tab:

   ![Avro Input Sample Lookup Fields Config](/files/UQPL6AJoMxYleQ5U5kIy)
8. Click **Preview** to view the data.

   You should see results similar to the results shown below:

   ![Avro Input Sample Preview Data](/files/Xl9MioQwcmQ3uJKd6cPo)
9. Save your transformation.


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