5. The product search method of claim 4 , wherein the searching of the database further comprises: separating the original query into a plurality of tokens using a predetermined engine indexer, searching the database using the tokens, and generating a fourth search result when an addition of the number of the first search results, the number of the second search results, and the number of the third search results is less than the reference value, and the product identifier that matches the original query includes the fourth search result.
5. The product search method of claim 4 , wherein the searching of the database further comprises: separating the original query into a plurality of tokens using a predetermined engine indexer, searching the database using the tokens, and generating a fourth search result when an addition of the number of the first search results, the number of the second search results, and the number of the third search results is less than the reference value, and the product identifier that matches the original query includes the fourth search result. 6. The product search method of claim 5 , wherein the searching of the database further comprises: generating a fifth search result including at least one token in the database, when an addition of the number of the first search results, the number of the second search results, the number of the third search results, and the number of the fourth search results is less than the reference value, and the product identifier that matches the original query includes the fifth search result.