SELECT 
  combination 
FROM 
  cscart_product_options_inventory 
WHERE 
  product_id = 750 
  AND amount > 0 
  AND combination != ''

Query time 0.00086

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_product_options_inventory range pc pc 770 82 Using index condition; Using where

Result

combination
1188_22396_1156_21888_1189_22398_1187_22389
1188_22396_1156_21888_1189_22398_1187_22390
1188_22396_1156_21888_1189_22399_1187_22389
1188_22396_1156_21888_1189_22399_1187_22390
1188_22396_1156_21888_1189_22400_1187_22389
1188_22396_1156_21888_1189_22400_1187_22390
1188_22396_1156_21888_1189_22401_1187_22389
1188_22396_1156_21888_1189_22401_1187_22390
1188_22396_1156_21888_1189_22402_1187_22389
1188_22396_1156_21888_1189_22402_1187_22390
1188_22396_1156_21888_1189_22404_1187_22389
1188_22396_1156_21888_1189_22404_1187_22390
1188_22396_1156_21888_1189_22405_1187_22389
1188_22396_1156_21888_1189_22405_1187_22390
1188_22396_1156_21888_1189_22406_1187_22389
1188_22396_1156_21888_1189_22406_1187_22390
1188_22396_1156_21888_1189_22408_1187_22389
1188_22396_1156_21888_1189_22408_1187_22390
1188_22396_1156_21888_1189_22409_1187_22389
1188_22396_1156_21888_1189_22409_1187_22390
1188_22396_1156_21888_1189_22410_1187_22389
1188_22396_1156_21888_1189_22410_1187_22390
1188_22396_1156_21888_1189_22411_1187_22389
1188_22396_1156_21888_1189_22411_1187_22390
1188_22397_1156_21888_1189_22398_1187_22389
1188_22397_1156_21888_1189_22398_1187_22390
1188_22397_1156_21888_1189_22399_1187_22389
1188_22397_1156_21888_1189_22399_1187_22390
1188_22397_1156_21888_1189_22400_1187_22389
1188_22397_1156_21888_1189_22400_1187_22390
1188_22397_1156_21888_1189_22401_1187_22389
1188_22397_1156_21888_1189_22401_1187_22390
1188_22397_1156_21888_1189_22402_1187_22389
1188_22397_1156_21888_1189_22402_1187_22390
1188_22397_1156_21888_1189_22402_1187_22394
1188_22397_1156_21888_1189_22403_1187_22389
1188_22397_1156_21888_1189_22403_1187_22390
1188_22397_1156_21888_1189_22404_1187_22389
1188_22397_1156_21888_1189_22404_1187_22390
1188_22397_1156_21888_1189_22405_1187_22389
1188_22397_1156_21888_1189_22405_1187_22390
1188_22397_1156_21888_1189_22405_1187_22393
1188_22397_1156_21888_1189_22405_1187_22394
1188_22397_1156_21888_1189_22406_1187_22389
1188_22397_1156_21888_1189_22406_1187_22390
1188_22397_1156_21888_1189_22406_1187_22393
1188_22397_1156_21888_1189_22407_1187_22389
1188_22397_1156_21888_1189_22407_1187_22390
1188_22397_1156_21888_1189_22408_1187_22389
1188_22397_1156_21888_1189_22408_1187_22390
1188_22397_1156_21888_1189_22409_1187_22389
1188_22397_1156_21888_1189_22409_1187_22390
1188_22397_1156_21888_1189_22410_1187_22389
1188_22397_1156_21888_1189_22410_1187_22390
1188_22397_1156_21888_1189_22411_1187_22389
1188_22397_1156_21888_1189_22411_1187_22390
1188_22397_1156_21888_1189_22412_1187_22389
1188_22397_1156_21888_1189_22412_1187_22390