The chapter discusses the evaluation techniques for query processing in large databases, emphasizing the need for efficient algorithms to handle complex and large datasets. It highlights that modern data models, such as object-oriented and extensible databases, do not solve the problem of managing large volumes of data; instead, they exacerbate it. The survey covers a wide range of practical query evaluation techniques, including iterative execution of complex query plans, the duality of sort- and hash-based set-matching algorithms, types of parallel query execution, and special operators for emerging database application domains. The chapter also delves into the architecture of query execution engines, sorting and hashing, disk access, aggregation and duplicate removal, binary matching operations, universal quantification, and the execution of complex query plans. It explores mechanisms for parallel query execution, including architectural issues and load balancing, and discusses specific parallel algorithms. Additionally, it outlines nonstandard operators for emerging database applications and additional techniques for performance improvement, such as precomputation, data compression, and specialized hardware. The chapter concludes with a summary and an outlook on query processing research and its future.The chapter discusses the evaluation techniques for query processing in large databases, emphasizing the need for efficient algorithms to handle complex and large datasets. It highlights that modern data models, such as object-oriented and extensible databases, do not solve the problem of managing large volumes of data; instead, they exacerbate it. The survey covers a wide range of practical query evaluation techniques, including iterative execution of complex query plans, the duality of sort- and hash-based set-matching algorithms, types of parallel query execution, and special operators for emerging database application domains. The chapter also delves into the architecture of query execution engines, sorting and hashing, disk access, aggregation and duplicate removal, binary matching operations, universal quantification, and the execution of complex query plans. It explores mechanisms for parallel query execution, including architectural issues and load balancing, and discusses specific parallel algorithms. Additionally, it outlines nonstandard operators for emerging database applications and additional techniques for performance improvement, such as precomputation, data compression, and specialized hardware. The chapter concludes with a summary and an outlook on query processing research and its future.