The current amount of text data in relational databases is massive and is growing fast. This increases the importance and need for non-technical users to be able to search for such information using a simple keyword search. Researchers have studied and addressed some of the issues with the efficiency and effectiveness of answering keyword queries in relational databases. In this paper we have summarized different factors affecting the effectiveness of the keyword search in relational databases which were studied in the early works. We have also identified two other important factors, namely keywords proximity and keywords N-grams that can further improve the search effectiveness when incorporated in the existing state-of-the-art information retrieval relevance ranking strategies for relational databases. Our experiments show that applying these two factors to the current ranking functions will improve the effectiveness of keyword search in relational databases.