A data engineer appends data to an existing Delta table using the following code. The DataFrame `df_new` has an extra column `discount_pct` that does not exist in the current table schema. What is the default behavior?

```python
df_new.write \
.format("delta") \
.mode("append") \
.save("/mnt/delta/orders")
```

Question

A data engineer appends data to an existing Delta table using the following code. The DataFrame `df_new` has an extra column `discount_pct` that does not exist in the current table schema. What is the default behavior?

```python
df_new.write \
    .format("delta") \
    .mode("append") \
    .save("/mnt/delta/orders")
```

Accepted Answer

B. The write fails with an `AnalysisException` because Delta Lake enforces schema by default. Delta Lake enforces schema by default (schema enforcement). When you attempt to append a DataFrame with a column not present in the existing table schema, Delta raises an `AnalysisException`. To allow schema evolution, you must use the `.option(\mergeSchema\, 	rue\)` write option or set the Spark config `spark.databricks.delta.schema.autoMerge.enabled` to `true`.

A data engineer appends data to an existing Delta table using the following code. The DataFrame `df_new` has an extra column `discount_pct` that does not exist in the current table schema. What is the default behavior?
`df_new.write \ .format("delta") \ .mode("append") \ .save("/mnt/delta/orders")`

Related Questions

Discussion

A data engineer appends data to an existing Delta table using the following code. The DataFrame df_new has an extra column discount_pct that does not exist in the current table schema. What is the default behavior? df_new.write \ .format("delta") \ .mode("append") \ .save("/mnt/delta/orders")

Related Questions

Discussion

A data engineer appends data to an existing Delta table using the following code. The DataFrame `df_new` has an extra column `discount_pct` that does not exist in the current table schema. What is the default behavior?
`df_new.write \ .format("delta") \ .mode("append") \ .save("/mnt/delta/orders")`