Databricks Certified Data Engineer - Associate

Explanation

The correct answer is B because:

1. UNION operator in SQL combines the result sets of two or more SELECT statements and removes duplicate rows by default.
2. The requirement is to create a table containing all records from both tables without duplicate records.
3. UNION performs exactly this operation - it combines all rows from both tables and eliminates duplicates.

Let's analyze why the other options are incorrect:

• A (INNER JOIN): This performs a join operation, not a union. It requires a join condition and returns only matching rows from both tables, not all records.

• C (OUTER JOIN): This also performs a join operation (likely meant to be FULL OUTER JOIN) and requires a join condition. It returns matching rows plus non-matching rows from both tables, but still requires a join condition and doesn't combine all records in the way UNION does.

• D (INTERSECT): This returns only the rows that appear in both tables (common rows), not all records from both tables.

• E (MERGE): MERGE is used for upsert operations (update/insert) based on matching conditions, not for combining all records from two tables.

Note: The SQL syntax in option B has a minor issue - it should be UNION SELECT * FROM april_transactions (with proper table name spacing), but conceptually it's the correct approach. In proper SQL, it would be:

CREATE TABLE all_transactions AS
SELECT * FROM march_transactions
UNION
SELECT * FROM april_transactions;

CREATE TABLE all_transactions AS
SELECT * FROM march_transactions
UNION
SELECT * FROM april_transactions;

Key SQL Operators:

• UNION: Combines results, removes duplicates
• UNION ALL: Combines results, keeps duplicates
• INTERSECT: Returns common rows only
• EXCEPT/MINUS: Returns rows from first query not in second