为什么此查询重复结果？

关于联接表，我不是很有经验，所以这可能是我联接它们的方式的结果。我不太明白为什么这个查询会重复结果。例如，这应该只返回3个结果，因为对于该特定的作业和修订版，我只有3行，但是返回6，则重复项与前3个完全相同。

          SELECT
               checklist_component_stock.id,
               checklist_component_stock.job_num,
               checklist_revision.user_id,
               checklist_component_stock.revision,
               checklist_category.name as category,
               checklist_revision.revision_num as revision_num,
               checklist_revision.category as rev_category,
               checklist_revision.per_workorder_number as per_wo_num,
               checklist_component_stock.wo_num_and_date,
               checklist_component_stock.posted_date,
               checklist_component_stock.comp_name_and_number,
               checklist_component_stock.finish_sizes,
               checklist_component_stock.material,
               checklist_component_stock.total_num_pieces,
               checklist_component_stock.workorder_num_one,
               checklist_component_stock.notes_one,
               checklist_component_stock.signoff_user_one,
               checklist_component_stock.workorder_num_two,
               checklist_component_stock.notes_two,
               checklist_component_stock.signoff_user_two,
               checklist_component_stock.workorder_num_three,
               checklist_component_stock.notes_three,
               checklist_component_stock.signoff_user_three
               FROM checklist_component_stock
               LEFT JOIN checklist_category ON checklist_component_stock.category
               LEFT JOIN checklist_revision ON checklist_component_stock.revision = checklist_revision.revision_num
               WHERE checklist_component_stock.job_num = 1000 AND revision = 1;

表结构：

checklist_category

checklist_revision

checklist_component_stock