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SELECT 
  product_id, 
  group_id 
FROM 
  cscart_product_variation_group_products 
WHERE 
  group_id IN (43, 29, 52, 33, 53, 45)

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_variation_group_products",
      "access_type": "index",
      "possible_keys": ["idx_group_id"],
      "key": "PRIMARY",
      "key_length": "6",
      "used_key_parts": ["product_id", "group_id"],
      "rows": 126,
      "filtered": 23.01587296,
      "attached_condition": "cscart_product_variation_group_products.group_id in (43,29,52,33,53,45)",
      "using_index": true
    }
  }
}

Result

product_id	group_id
127	53
128	43
132	52
134	33
135	29
137	45
200	29
201	29
202	29
203	29
204	29
219	33
220	33
221	33
222	33
223	33
256	43
257	43
260	45
261	45
262	45
263	45
264	45
283	52
284	52
285	53
286	53

product_id	group_id
127	53
128	43
132	52
134	33
135	29
137	45
200	29
201	29
202	29
203	29
204	29
219	33
220	33
221	33
222	33
223	33
256	43
257	43
260	45
261	45
262	45
263	45
264	45
283	52
284	52
285	53
286	53

product_id	group_id
127	53
128	43
132	52
134	33
135	29
137	45
200	29
201	29
202	29
203	29
204	29
219	33
220	33
221	33
222	33
223	33
256	43
257	43
260	45
261	45
262	45
263	45
264	45
283	52
284	52
285	53
286	53

product_id	group_id
127	53
128	43
132	52
134	33
135	29
137	45
200	29
201	29
202	29
203	29
204	29
219	33
220	33
221	33
222	33
223	33
256	43
257	43
260	45
261	45
262	45
263	45
264	45
283	52
284	52
285	53
286	53