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A data engineering team has two tables. The first table march_transactions is a collection of all retail transactions in the month of March. The second table april_transactions is a collection of all retail transactions in the month of April. There are no duplicate records between the tables. Which of the following commands should be run to create a new table all_transactions that contains all records from march_transactions and april_transactions without duplicate records?
Real Exam
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KKeng
A
CREATE TABLE all_transactions AS SELECT * FROM march_transactions INNER JOIN SELECT * FROM april_transactions;
B
CREATE TABLE all_transactions AS SELECT * FROM march_transactions UNION SELECT * FROM april_transactions;
C
CREATE TABLE all_transactions AS SELECT * FROM march_transactions OUTER JOIN SELECT * FROM april_transactions;
D
CREATE TABLE all_transactions AS SELECT * FROM march_transactions INTERSECT SELECT * FROM april_transactions;
E
CREATE TABLE all_transactions AS SELECT * FROM march_transactions MERGE SELECT * FROM april_transactions;
Explanation:
The UNION operator is the correct choice because:
- UNION combines result sets from multiple SELECT statements into a single result set
- UNION automatically removes duplicates - which is exactly what's needed since the requirement is to have all records without duplicates
- The problem states there are no duplicate records between tables, but UNION ensures no duplicates even if there were
Why other options are incorrect:
- A (INNER JOIN): This performs a join operation based on matching columns, not a union of all records
- C (OUTER JOIN): This also performs a join operation, not a union of all records
- D (INTERSECT): This returns only records that exist in BOTH tables, not all records from both tables
- E (MERGE): MERGE is used for upsert operations (UPDATE/INSERT), not for combining all records from two tables
Note: In SQL, UNION ALL would keep duplicates, but UNION removes duplicates. Since the requirement is "without duplicate records," UNION is the correct choice.
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