Tham khảo tài liệu 'giáo trình sql bài 15', công nghệ thông tin, cơ sở dữ liệu phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Lecture 7 SQL 2 - Select Grouping data 0 UNIVERSITY Objectives More Complex SQL Queries Nesting Of Queries Exists Function Nulls Joined Relation Aggregate Functions Grouping - Having Clause Substring Comparison - Arithmetic Operations Order By Clause Reference Chapter 8 Faculty of Science and Technology Database Fundamentals 2 UNIVERSITY Set Operations SQL has directly incorporated some set operations There is a union operation UNION and in some versions of SQL there are set difference MINUS and intersection INTERSECT operations The resulting relations of these set operations are sets of tuples duplicate tuples are eliminated from the result The set operations apply only to union compatible relations the two relations must have the same attributes and the attributes must appear in the same order Faculty of Science and Technology Database Fundamentals
