Keyword search over databases, popularized by keyword search in WWW, allows ordinary users to access database information without the knowledge of structured query languages and database schemas. Most of the previous studies in this area use IR-style ranking, which fail to consider the importance of the query answers. In this paper, we propose CI-RANK, a new approach for keyword search in databases, which considers the importance of individual nodes in a query answer and the cohesiveness of the result structure in a balanced way. CI-RANK is built upon a carefully designed model call Random Walk with Message Passing that helps capture the relationships between different nodes in the query answer. We develop a branch and bound algorithm to support the efficient generation of top-k query answers. Indexing methods are also introduced to further speed up the run-time processing of queries. Extensive experiments conducted on two real data sets with a real user query log confirm the effectiveness and efficiency of CI-RANK.