Thanks. Still giving data mismatch error -

table : account
account_dimension_id BIGINT GENERATED BY DEFAULT AS IDENTITY,

df = spark.read.format("csv").option("header", "true").load("abfss://databricks-storage@sa14127e1dv0101.dfs.core.windows.net/catalogs/data-relationship-management-drm/onprem_acct_dimension.csv")
for col in df.columns:
df = df.withColumnRenamed(col, col.lower())
display(df)
df.write.format("delta").mode("append").option("mergeSchema", "true").saveAsTable("account")

Error:
[DELTA_FAILED_TO_MERGE_FIELDS] Failed to merge fields 'insert_date' and 'insert_date' SQLSTATE: 22005
File <command-2201570317935975>, line 8
 df = df.withColumnRenamed(col, col.lower())