SQL UNION Across Tables | Dataford Interview Questions

Write a SQL UNION query to combine data from three tables sharing the same unique ID.

Use the three supplied tables and return the combined distinct records. Preserve NULL status values and produce deterministic ordering.

Output

One row per distinct unique_id and record_status combination
Columns: unique_id, record_status
Sort by unique_id ascending, then record_status ascending with NULL values last

source_a_records

Column	Type	Description
unique_idPK	INT	Unique identifier for the record
record_status	VARCHAR(30)	Status associated with the record

source_b_records

Column	Type	Description
unique_idPK	INT	Unique identifier for the record
record_status	VARCHAR(30)	Status associated with the record

source_c_records

Column	Type	Description
unique_idPK	INT	Unique identifier for the record
record_status	VARCHAR(30)	Status associated with the record

Your question is SQL UNION Across Tables. Start with the requirements and the three tables in the Question tab.

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