LEFT vs INNER JOIN for Parts

Context

In manufacturing reporting, you often need to decide whether unmatched records should stay in the result set. This matters when some Lucid Air or Gravity parts have not yet been assigned to an assembly line.

Core question

Explain the difference between an INNER JOIN and a LEFT JOIN using a scenario with vehicle_parts and assembly_lines, where some parts do not yet have an assigned line. Describe which rows each join returns, how NULL values appear in the result, and when you would choose one join over the other.

Scope guidance

You should answer at an interview-ready level: define both join types clearly, walk through a small example, and explain the business implication of excluding versus retaining unassigned parts in an operational report.