SET @col_exists := (
  SELECT COUNT(1)
  FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = DATABASE()
    AND TABLE_NAME = 'orders'
    AND COLUMN_NAME = 'canceled_at'
);
SET @sql := IF(
  @col_exists = 0,
  'ALTER TABLE orders ADD COLUMN canceled_at DATETIME NULL AFTER locked_at',
  'SELECT 1'
);
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

SET @col_exists := (
  SELECT COUNT(1)
  FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = DATABASE()
    AND TABLE_NAME = 'orders'
    AND COLUMN_NAME = 'cancel_note'
);
SET @sql := IF(
  @col_exists = 0,
  'ALTER TABLE orders ADD COLUMN cancel_note TEXT NULL AFTER cancel_reason',
  'SELECT 1'
);
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

SET @col_exists := (
  SELECT COUNT(1)
  FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = DATABASE()
    AND TABLE_NAME = 'orders'
    AND COLUMN_NAME = 'canceled_by_name_snapshot'
);
SET @sql := IF(
  @col_exists = 0,
  'ALTER TABLE orders ADD COLUMN canceled_by_name_snapshot VARCHAR(190) NULL AFTER canceled_by',
  'SELECT 1'
);
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

SET @col_exists := (
  SELECT COUNT(1)
  FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = DATABASE()
    AND TABLE_NAME = 'orders'
    AND COLUMN_NAME = 'canceled_by'
);
SET @sql := IF(
  @col_exists = 0,
  'ALTER TABLE orders ADD COLUMN canceled_by BIGINT UNSIGNED NULL AFTER canceled_at',
  'SELECT 1'
);
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

SET @col_exists := (
  SELECT COUNT(1)
  FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = DATABASE()
    AND TABLE_NAME = 'orders'
    AND COLUMN_NAME = 'cancel_reason'
);
SET @sql := IF(
  @col_exists = 0,
  'ALTER TABLE orders ADD COLUMN cancel_reason VARCHAR(255) NULL AFTER canceled_by',
  'SELECT 1'
);
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;