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SELECT 
  a.modifier, 
  a.modifier_type, 
  IF(
    shared_option_variants.variant_id IS NOT NULL, 
    shared_option_variants.modifier, 
    a.modifier
  ) as modifier, 
  IF(
    shared_option_variants.variant_id IS NOT NULL, 
    shared_option_variants.modifier_type, 
    a.modifier_type
  ) as modifier_type, 
  a.variant_id 
FROM 
  cscart_product_option_variants a 
  LEFT JOIN cscart_ult_product_option_variants shared_option_variants ON shared_option_variants.variant_id = a.variant_id 
  AND shared_option_variants.company_id = 1 
WHERE 
  1 
  AND a.variant_id IN (
    239345, 236687, 233494, 240507, 240536, 
    240559, 240582, 233635, 230381, 224224, 
    223755, 239426
  )

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "shared_option_variants",
      "access_type": "system",
      "possible_keys": ["PRIMARY", "company_id"],
      "rows": 0,
      "filtered": 0,
      "const_row_not_found": true
    },
    "table": {
      "table_name": "a",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["variant_id"],
      "rows": 12,
      "filtered": 100,
      "attached_condition": "a.variant_id in (239345,236687,233494,240507,240536,240559,240582,233635,230381,224224,223755,239426)"
    }
  }
}

Result

modifier	modifier_type	variant_id
0.000	A	223755
0.000	A	224224
0.000	A	230381
0.000	A	233494
0.000	A	233635
0.000	A	236687
0.000	A	239345
0.000	A	239426
0.000	A	240507
0.000	A	240536
0.000	A	240559
0.000	A	240582