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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 (
    218033, 237344, 232807, 236103, 236129, 
    236156, 233233, 232817, 232828, 232839, 
    232908, 232921, 232268, 236170, 236196, 
    221143
  )

Query time 0.00047

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": 16,
      "filtered": 100,
      "attached_condition": "a.variant_id in (218033,237344,232807,236103,236129,236156,233233,232817,232828,232839,232908,232921,232268,236170,236196,221143)"
    }
  }
}

Result

modifier	modifier_type	variant_id
0.000	A	218033
0.000	A	221143
0.000	A	232268
0.000	A	232807
0.000	A	232817
0.000	A	232828
0.000	A	232839
0.000	A	232908
0.000	A	232921
0.000	A	233233
0.000	A	236103
0.000	A	236129
0.000	A	236156
0.000	A	236170
0.000	A	236196
0.000	A	237344