Raghu ramakrishnan is the best reference book for solving DBMS related queries like algebra queries, SQL queries. this book ie eaisly explained about algebra, SQL queries in detailed. I am a student of computer science engineering. I also refer this book for learning DBMS query. because only this book give many example of queries solved and unsolved both type.
And give also many practice question in easy language. now I can solve algebra and SQL both type of queries. this is the best book for solving database management system related queries. I suggest to all for raghu ramakrishnan book.