[FAQ Bot] NEW: Why are there unexpected years in lpep_pickup_datetime after loading tax (#194)

* NEW: Why are there unexpected years in lpep_pickup_datetime after loading tax

* Fix filename slug and sort order for BigQuery timestamp FAQ

---------

Co-authored-by: FAQ Bot <faq-bot@datatalks.club>
Co-authored-by: Alexey Grigorev <alexey.s.grigoriev@gmail.com>

Author: 3 people

_questions/data-engineering-zoomcamp/module-3/049_52e74f0053_unexpected-years-lpep-pickup-datetime-bigquery.md

@@ -0,0 +1,36 @@
+---
+id: 52e74f0053
+question: Why are there unexpected years in lpep_pickup_datetime after loading taxi
+  data into BigQuery?
+sort_order: 49
+---
+
+Unexpected years in lpep_pickup_datetime after loading taxi data into BigQuery usually indicate a corrupted or incorrect load. Common causes include:
+
+- CSV schema autodetect misinterpreting timestamp format
+- Mixing Parquet and CSV loads into the same table
+- Appending instead of replacing during reload
+- Partial failed loads
+
+How to verify:
+
+- Run a range check:
+
+```sql
+SELECT
+  MIN(lpep_pickup_datetime),
+  MAX(lpep_pickup_datetime)
+FROM `project.dataset.table`;
+```
+
+If the values fall outside the expected years (for example 2019–2020), reload the table from a clean source using a replacement load, preferably Parquet:
+
+```bash
+bq load \
+  --source_format=PARQUET \
+  --replace \
+  dataset.table \
+  gs://bucket/path/*.parquet
+```
+
+Note: Using Parquet instead of CSV often helps prevent schema interpretation issues and ensures a cleaner, replace-based reload.