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 # Electricity Price Data
 * For each month from 2017/01 to the latest available month, fetch the zipfile data from the source site via API, extract all csv files inside the zipfile, and concatenate them.
 * Create the table in Big Query from the first month(2017/01) only.
-* Append data to the table from 2017/02 up to the latest available month.
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+* Append data to the table from 2017/02 up to the latest available month.
+
+# Henry Hub Natural Gas Data
+* Use a truncate-and-load (full refresh) strategy.
+* For each run, fetch the full daily Henry Hub series from the EIA API, starting from 1993/12/24 up to the latest available date.
+* Keep the relevant fields, clean the data, and replace the BigQuery table each time using `if_exists="replace"`.
+* This strategy is appropriate because the Henry Hub dataset is relatively small and stable, so a full refresh is simpler and more reliable than incremental loading. It avoids the extra complexity of tracking the last loaded date, handling reruns, and preventing duplicate rows. As a result, the BigQuery table always contains one clean and up-to-date version of the source data.