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SELECT 
  product_id, 
  group_id 
FROM 
  cscart_product_variation_group_products 
WHERE 
  group_id IN (49, 25, 19, 32, 37)

Query time 0.00025

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": 17.46031761,
      "attached_condition": "cscart_product_variation_group_products.group_id in (49,25,19,32,37)",
      "using_index": true
    }
  }
}

Result

product_id	group_id
111	32
133	49
136	19
139	25
177	37
179	19
180	19
191	25
192	25
211	32
212	32
213	32
214	32
215	32
216	32
217	32
218	32
233	37
234	37
277	49
278	49

product_id	group_id
111	32
133	49
136	19
139	25
177	37
179	19
180	19
191	25
192	25
211	32
212	32
213	32
214	32
215	32
216	32
217	32
218	32
233	37
234	37
277	49
278	49

product_id	group_id
111	32
133	49
136	19
139	25
177	37
179	19
180	19
191	25
192	25
211	32
212	32
213	32
214	32
215	32
216	32
217	32
218	32
233	37
234	37
277	49
278	49

product_id	group_id
111	32
133	49
136	19
139	25
177	37
179	19
180	19
191	25
192	25
211	32
212	32
213	32
214	32
215	32
216	32
217	32
218	32
233	37
234	37
277	49
278	49