数据库系统原理(英文)-4-13(精品·公开课件).ppt

March 2013 Database System Concepts - Chapter4 Advanced SQL - PART 2 RELATIONAL DATABASES Chapter 4 Advanced SQL Integrity constraints in SQL §4.1-4.2 Security in SQL (§4.3) authorization, grant/revoke Embedded and dynamic SQL §4.4-4.5 4.1.1 Built-in Data Types in SQL In addition to the basic data types, e.g. char(n), varchar(n), int, smallint, numeric(p, d), real, double precision, float(n), described in §3.2, the other built-in data types include date: Dates, containing a (4 digit) year, month and date e.g. date ‘2005-7-27 time: Time of day, in hours, minutes and seconds e.g. time ‘09:00:30.75 timestamp: date plus time of day e.g. timestamp ‘2005-7-27 09:00:30.75’ interval: period of time e.g. interval ‘1’ day Subtracting a date/time/timestamp value from another gives an interval value interval values can be added to date/time/timestamp values Values of individual fields can be extracted from date/time/timestamp e.g. extract (year from r.starttime) We can cast /convert string types to date/time/timestamp e.g. cast string-valued-expression as date e.g. cast string-valued-expression as time The create type clause can be used to define new user-defined types e.g. create type Dollars as numeric (12,2) final The create domain clause can be used to define new user-defined domains e.g. create domain person_name char(20) not null 4.1.3 Large-Object Types Large objects (photos, videos, CAD files, etc.) are stored as a large object blob: binary large object the object is a large collection of uninterpreted binary data, whose interpretation is left to an application outside of the database system clob: character large object the object is a large collection of character data When a query returns a large object, a pointer is returned rather than the large object itself. 4.1.3 Large-Object Types (cont.) E.g. book_view clob(10KB) image blob(10MB) movie blob(2GB) Now, Oracle, DB2, and SQL Server also support the XML da