Existing exam tables: exam_attempt_answers, exam_attempts, exam_materials, exam_questions, exam_sets

Table: exam_materials
------------------------------------------------------------
  id                        int(10) unsigned     NOT NULL  AUTO_INCREMENT
  original_filename         varchar(255)         NOT NULL  
  stored_filename           varchar(255)         NOT NULL  
  file_extension            varchar(10)          NOT NULL  
  mime_type                 varchar(127)         NOT NULL  
  file_size                 int(10) unsigned     NOT NULL  
  extracted_text            longtext             NULL  
  structured_content_json   longtext             NULL  
  status                    enum('uploaded','text_extracted','questions_generated','failed') NOT NULL DEFAULT uploaded 
  error_message             text                 NULL  
  created_at                datetime             NOT NULL DEFAULT current_timestamp() 
  Indexes:
    - UNIQUE PRIMARY (id)
    - idx_em_status (status)
    - idx_em_created_at (created_at)

Table: exam_sets
------------------------------------------------------------
  id                        int(10) unsigned     NOT NULL  AUTO_INCREMENT
  material_id               int(10) unsigned     NOT NULL  
  set_number                int(10) unsigned     NOT NULL  
  requested_count           int(10) unsigned     NOT NULL DEFAULT 50 
  generated_count           int(10) unsigned     NOT NULL DEFAULT 0 
  skipped_duplicate_count   int(10) unsigned     NOT NULL DEFAULT 0 
  status                    enum('requested','generated','partial','failed') NOT NULL DEFAULT requested 
  error_message             text                 NULL  
  created_at                datetime             NOT NULL DEFAULT current_timestamp() 
  rejected_invalid_count    int(10) unsigned     NOT NULL DEFAULT 0 
  Indexes:
    - UNIQUE PRIMARY (id)
    - UNIQUE uq_es_material_set_number (material_id)
    - UNIQUE uq_es_material_set_number (set_number)
    - idx_es_material_id (material_id)
    - idx_es_set_number (set_number)
    - idx_es_status (status)

Table: exam_questions
------------------------------------------------------------
  id                        int(10) unsigned     NOT NULL  AUTO_INCREMENT
  material_id               int(10) unsigned     NOT NULL  
  exam_set_id               int(10) unsigned     NOT NULL  
  question                  text                 NOT NULL  
  option_a                  text                 NOT NULL  
  option_b                  text                 NOT NULL  
  option_c                  text                 NOT NULL  
  option_d                  text                 NOT NULL  
  correct_option            enum('A','B','C','D') NOT NULL  
  explanation               text                 NULL  
  source_location           varchar(255)         NOT NULL  
  source_quote              text                 NULL  
  topic                     varchar(150)         NULL  
  difficulty                enum('easy','medium','hard') NULL DEFAULT medium 
  question_hash             char(64)             NULL  
  sort_order                int(10) unsigned     NOT NULL DEFAULT 0 
  created_at                datetime             NOT NULL DEFAULT current_timestamp() 
  Indexes:
    - UNIQUE PRIMARY (id)
    - idx_eq_material_id (material_id)
    - idx_eq_exam_set_id (exam_set_id)
    - idx_eq_question_hash (question_hash)

Table: exam_attempts
------------------------------------------------------------
  id                        int(10) unsigned     NOT NULL  AUTO_INCREMENT
  exam_set_id               int(10) unsigned     NOT NULL  
  material_id               int(10) unsigned     NOT NULL  
  started_at                datetime             NULL  
  expires_at                datetime             NULL  
  submitted_at              datetime             NULL  
  status                    enum('not_started','in_progress','submitted','auto_submitted','expired') NOT NULL DEFAULT not_started 
  score                     int(10) unsigned     NULL  
  total_questions           int(10) unsigned     NOT NULL DEFAULT 0 
  answered_count            int(10) unsigned     NOT NULL DEFAULT 0 
  created_at                datetime             NOT NULL DEFAULT current_timestamp() 
  Indexes:
    - UNIQUE PRIMARY (id)
    - idx_ea_exam_set_id (exam_set_id)
    - idx_ea_material_id (material_id)
    - idx_ea_status (status)

Table: exam_attempt_answers
------------------------------------------------------------
  id                        int(10) unsigned     NOT NULL  AUTO_INCREMENT
  attempt_id                int(10) unsigned     NOT NULL  
  question_id               int(10) unsigned     NOT NULL  
  selected_option           enum('A','B','C','D') NULL  
  is_correct                tinyint(1)           NULL  
  answered_at               datetime             NULL  
  created_at                datetime             NOT NULL DEFAULT current_timestamp() 
  Indexes:
    - UNIQUE PRIMARY (id)
    - UNIQUE uq_eaa_attempt_question (attempt_id)
    - UNIQUE uq_eaa_attempt_question (question_id)
    - idx_eaa_attempt_id (attempt_id)
    - idx_eaa_question_id (question_id)

All expected Exam Prep tables verified.