Tham khảo tài liệu 'an introduction to database systems 8ed - c j date - solutions manual episode 2 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | SELECT MAX AS MAXSAL MIN AS MINSAL FROM STATS GROUP BY GRANT SELECT ON JOBMAXMIN TO King a. REVOKE SELECT ON STATS FROM Ford RESTRICT b. REVOKE INSERT DELETE ON STATS FROM Smith RESTRICT c. REVOKE SELECT ON MINE FROM PUBLIC RESTRICT d. REVOKE SELECT UPDATE SALARY TAX ON STATS FROM Nash RESTRICT e. REVOKE SELECT NAME SALARY TAX ON STATS FROM Todd RESTRICT f. REVOKE SELECT NAME SALARY TAX UPDATE SALARY TAX ON STATS FROM Ward RESTRICT g. REVOKE ALL PRIVILEGES ON PREACHERS FROM Pope RESTRICT h. REVOKE DELETE ON NONSPECIALIST FROM Jones RESTRICT i. REVOKE SELECT ON JOBMAXMIN FROM King RESTRICT End of Chapter 17 Copyright c 2003 C. J. Date page Chapter 18 O p t i m i z a t i o n Principal Sections A motivating example An overview of query processing Expression transformation DB statistics A divide-and-conquer strategy Implementing the relational operators General Remarks No SQL Facilities section in this chapter. However some SQL-specific optimization issues are discussed in the annotation to several of the references especially references . Also the summary section mentions the fact that 3VL SQL s flawed support for 3VL and duplicate rows all serve as optimization inhibitors and the same is true for SQL s left-to-right column ordering though this last one isn t mentioned in the chapter itself . The articles mentioned under reference are also relevant. The material of this chapter is stuff that in principle given a perfect system the user really shouldn t need to know about. It s part of the implementation not part of the model. However just as a knowledge of what goes on under the hood can help you be a better driver a knowledge of what s involved in executing queries might help you use the system better. In any case it s interesting stuff and it s a major part of relational technology in general though not part of the relational model per se. The chapter really shouldn t be omitted .
