Securing Unity Catalog: Who Gets What

How Unity Catalog security works

Principals: who can access data

Principal Type	What It Is	Example
User	Individual human identity (synced from Microsoft Entra ID)	ravi.nair@datapulse.com
Service principal	Application identity for automated access	sp-etl-pipeline
Group	Collection of users and/or service principals	data-engineers, bi-analysts

Best practice: Always grant permissions to groups, not individual users. When Mei Lin onboards a new analyst at Freshmart, she adds them to the bi-analysts group — they instantly inherit all the right permissions.

Privilege hierarchy

Privileges flow down the Unity Catalog namespace:

Metastore
  └── Catalog (GRANT on catalog → inherits to all schemas/tables below)
        └── Schema (GRANT on schema → inherits to all tables below)
              └── Table / View / Volume / Function

Common privileges

Privilege	What It Allows	Securable Objects
SELECT	Read data	Table, View
MODIFY	Insert, update, delete data	Table
CREATE TABLE	Create tables within a schema	Schema
CREATE SCHEMA	Create schemas within a catalog	Catalog
USE CATALOG	Access objects in the catalog	Catalog
USE SCHEMA	Access objects in the schema	Schema
ALL PRIVILEGES	Full access	Any securable
EXECUTE	Run a function	Function

-- Grant a group permission to read all tables in a schema
GRANT USE CATALOG ON CATALOG prod_sales TO `bi-analysts`;
GRANT USE SCHEMA ON SCHEMA prod_sales.reports TO `bi-analysts`;
GRANT SELECT ON SCHEMA prod_sales.reports TO `bi-analysts`;

-- Grant a service principal full access to raw data
GRANT ALL PRIVILEGES ON SCHEMA prod_sales.raw TO `sp-etl-pipeline`;

-- Revoke access
REVOKE SELECT ON TABLE prod_sales.curated.customer_pii FROM `bi-analysts`;

💡 Exam tip: USE CATALOG + USE SCHEMA are required

A common exam trap: granting SELECT on a table is not enough. The principal also needs:

1. USE CATALOG on the parent catalog
2. USE SCHEMA on the parent schema
3. SELECT on the table

Without all three, the query fails with a “catalog not found” or “schema not found” error. The exam tests this with scenarios where a user has SELECT but can’t see the table.

Table and column-level access control

Column-level access

Restrict which columns specific users can see:

-- Analyst group can see orders but NOT customer_email or credit_card
GRANT SELECT (order_id, order_date, amount, region)
  ON TABLE prod_sales.curated.orders
  TO `bi-analysts`;

When a BI analyst queries the table, they only see the four granted columns. Attempting to SELECT customer_email returns an access denied error.

Row-level security

Row-level security filters rows based on who’s querying. Dr. Sarah Okafor uses this at Athena Group so each regional manager only sees their own region’s data:

-- Create a row filter function
CREATE FUNCTION prod_sales.functions.region_filter(region_col STRING)
RETURN IF(
  IS_ACCOUNT_GROUP_MEMBER('global-admins'),
  TRUE,  -- admins see everything
  region_col = CURRENT_USER_ATTRIBUTE('region')  -- others see only their region
);

-- Apply the row filter to a table
ALTER TABLE prod_sales.curated.daily_revenue
  SET ROW FILTER prod_sales.functions.region_filter ON (region);

Now when a user in the APAC group queries daily_revenue, they only see APAC rows. Global admins see all rows.

Compute access permissions

Compute resources also have access controls:

Permission	What It Allows
CAN ATTACH TO	Use the cluster to run notebooks
CAN RESTART	Restart the cluster
CAN MANAGE	Full control (configure, start, stop, delete)

Dr. Sarah Okafor grants:
- data-engineers group → CAN MANAGE on dev clusters
- bi-analysts group → CAN ATTACH TO on shared SQL warehouse
- sp-etl-pipeline → CAN ATTACH TO on job clusters

Exam tip: Compute permissions are separate from data permissions. A user needs BOTH compute access (to run queries) AND data access (to read tables).

Question

What three things does a user need to query a table in Unity Catalog?

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Answer

1) USE CATALOG on the parent catalog, 2) USE SCHEMA on the parent schema, 3) SELECT on the table. Missing any one of these causes an access denied error.

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Question

What is the difference between column-level access and row-level security?

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Answer

Column-level access restricts WHICH COLUMNS a user can see (GRANT SELECT on specific columns). Row-level security restricts WHICH ROWS a user can see (using a row filter function that evaluates per-user context).

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Question

Why should you grant permissions to groups rather than individual users?

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Answer

Groups simplify permission management — add/remove users from the group and they instantly inherit/lose permissions. Granting to individuals creates maintenance overhead and inconsistency as teams change.

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Knowledge check

Knowledge Check

A BI analyst at Freshmart reports they can't find the 'prod_sales' catalog when running queries. Mei Lin checks and confirms the analyst has SELECT on the table they need. What is the most likely cause?

AThe analyst is missing USE CATALOG and/or USE SCHEMA privilegesBThe analyst's Entra ID account is disabledCThe table has row-level security that filters out all rowsDThe analyst is using a SQL warehouse that doesn't support Unity Catalog

Check Answer

Knowledge Check

Dr. Sarah Okafor needs to ensure that each regional sales manager at Athena Group can only see data from their own region when querying the daily_revenue table. Global admins should see all regions. Which approach should she use?

ACreate separate tables per region (daily_revenue_apac, daily_revenue_emea)BCreate separate views per region with WHERE filtersCApply a row filter function that checks the querying user's group membershipDUse column-level access control to hide the region column

Check Answer

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Next up: Secrets & Authentication — Azure Key Vault integration, service principals, and managed identities.