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SELECT 
  b.variant_name, 
  a.*, 
  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 
FROM 
  cscart_product_option_variants AS a 
  LEFT JOIN cscart_product_option_variants_descriptions AS b ON b.variant_id = a.variant_id 
  AND b.lang_code = 'fr' 
  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.option_id IN (784, 770) 
  AND a.status = 'A' 
ORDER BY 
  a.position, 
  a.variant_id

Query time 0.00342

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "25.41"
    },
    "ordering_operation": {
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "9.00"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "shared_option_variants",
            "access_type": "system",
            "possible_keys": [
              "PRIMARY",
              "company_id"
            ],
            "rows_examined_per_scan": 0,
            "rows_produced_per_join": 1,
            "filtered": "0.00",
            "const_row_not_found": true,
            "cost_info": {
              "read_cost": "0.00",
              "eval_cost": "0.20",
              "prefix_cost": "0.00",
              "data_read_per_join": "24"
            },
            "used_columns": [
              "variant_id",
              "company_id",
              "modifier",
              "modifier_type"
            ]
          }
        },
        {
          "table": {
            "table_name": "a",
            "access_type": "range",
            "possible_keys": [
              "option_id",
              "option_id_2",
              "status"
            ],
            "key": "option_id",
            "used_key_parts": [
              "option_id",
              "status"
            ],
            "key_length": "6",
            "rows_examined_per_scan": 9,
            "rows_produced_per_join": 9,
            "filtered": "100.00",
            "index_condition": "((`ea201_diorama`.`a`.`option_id` in (784,770)) and (`ea201_diorama`.`a`.`status` = 'A'))",
            "cost_info": {
              "read_cost": "12.81",
              "eval_cost": "1.80",
              "prefix_cost": "14.61",
              "data_read_per_join": "432"
            },
            "used_columns": [
              "variant_id",
              "option_id",
              "position",
              "modifier",
              "modifier_type",
              "weight_modifier",
              "weight_modifier_type",
              "point_modifier",
              "point_modifier_type",
              "status"
            ]
          }
        },
        {
          "table": {
            "table_name": "b",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "variant_id",
              "lang_code"
            ],
            "key_length": "9",
            "ref": [
              "ea201_diorama.a.variant_id",
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 9,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.00",
              "eval_cost": "1.80",
              "prefix_cost": "16.41",
              "data_read_per_join": "6K"
            },
            "used_columns": [
              "variant_id",
              "lang_code",
              "variant_name"
            ]
          }
        }
      ]
    }
  }
}

Result

variant_name	variant_id	option_id	position	modifier	modifier_type	weight_modifier_type	point_modifier_type	status
Echelle 1:160 - 13 mm long	3127	770	1	0.000	A	A	A	A
Echelle 1:100 - 21 mm long	3128	770	2	0.000	A	A	A	A
Echelle 1:100 - 20 mm long	3241	784	2	0.000	A	A	A	A
Echelle 1:87 - 24 mm long	3130	770	3	0.000	A	A	A	A
Echelle 1:87 - 22 mm long	3242	784	3	0.000	A	A	A	A
Echelle 1:50 - 17 mm haut x 42 mm long	3132	770	4	0.500	A	A	A	A
Echelle 1:50 - 39 mm long x 14 mm large	3243	784	4	0.000	A	A	A	A
Echelle 1:43 - 48 mm long	3133	770	5	1.500	A	A	A	A
Echelle 1:43 - 45 mm long	3244	784	5	1.600	A	A	A	A
Echelle 1:32 - 65 mm long	3134	770	6	3.500	A	A	A	A
Echelle 1:32 - 60 mm long	3245	784	6	5.000	A	A	A	A
Echelle 1:22.5 - 86 mm long	3246	784	7	10.000	A	A	A	A
Echelle 1:25 - 82 mm long	3258	770	7	6.000	A	A	A	A
Echelle 1:22.5 - 90 mm long	3135	770	8	6.500	A	A	A	A