LEFT vs INNER Join With Nulls | Dataford Interview Questions

Explain the difference between a LEFT JOIN and an INNER JOIN in terms of performance and output when dealing with null values.

Use the provided State Farm policyholder and auto policy data to demonstrate both join results. Return the join type, policyholder details, and policy details, including unmatched policyholders.

Output

Columns: join_type, policyholder_id, policyholder_name, policy_id, policy_status
Include rows produced by both join types, labeled accordingly
Order by join_type, policyholder_id, and policy_id

Schema

policyholders

Column	Type	Description
policyholder_idPK	INT	Unique policyholder identifier
policyholder_name	VARCHAR(100)	Policyholder display name
state_code	VARCHAR(2)	Two-letter state code

auto_policies

Column	Type	Description
policy_idPK	INT	Unique auto policy identifier
policyholder_id	INT	Associated policyholder identifier
policy_status	VARCHAR(20)	Current policy status
coverage_type	VARCHAR(30)	Type of auto coverage

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