1. A data governance team wants to classify sensitive columns across all tables in a Unity Catalog metastore by attaching metadata labels such as `PII`, `CONFIDENTIAL`, and `INTERNAL`. Later, they need to programmatically discover all columns tagged `PII`. Which Unity Catalog capability supports this workflow?
- A. Delta Lake column comments set via `ALTER TABLE ... ALTER COLUMN ... COMMENT`.
- B. Unity Catalog system table `SYSTEM.INFORMATION_SCHEMA.COLUMNS` filtered on the `COMMENT` field.
- C. Unity Catalog tags applied via `ALTER TABLE ... ALTER COLUMN ... SET TAGS` and queried through `SYSTEM.INFORMATION_SCHEMA.COLUMN_TAGS`.✓ Correct
- D. Databricks lakehouse monitoring profiles attached to each table with a sensitivity classification field.
Explanation
Unity Catalog supports **tags** (key-value metadata) on catalog objects including columns. You apply them with `ALTER TABLE <t> ALTER COLUMN <c> SET TAGS ('classification' = 'PII')` and then discover tagged columns by querying `SYSTEM.INFORMATION_SCHEMA.COLUMN_TAGS`. **Option A** (column comments) are free-text annotations with no structured discovery mechanism — you cannot reliably filter or enforce them. **Option B** filtering `COMMENT` fields is fragile, unstructured, and not the intended governance mechanism; comments are not indexed or queryable as tags. **Option D** describes Databricks Lakehouse Monitoring, which produces data quality metrics and statistics — it has no sensitivity classification field and is unrelated to metadata tagging.