This book surveys recent development in the keyword search over databases, and focuses on finding the structural information between the objects in the database using a set of keywords. structural information must be returned to the form of trees or subgraphs represent how the object, which contains the keywords that are needed, are interconnected in a relational database or in XML databases. In Chapter 2, we focus on structural support keyword search in relational database management systems using SQL query language. In Chapter 3, we discuss graph algorithms for structural keyword searches by treating the entire relational database as a large data graph. In Chapter 4, we discuss structural keyword search in a large XML database tree-structured. Contents: Introduction / Schema-Based Keyword Search in Relational Database / Search Keyword Graph-Based / Keyword Search on XML Databases / Other topics to Search Keyword Databases