It uses operators to perform queries. Relational Algebra. it can be categorized as either procedural or nonprocedural. Types of Relational operation 1. In a procedural language the user instructs the system to do a sequence of operations on database to compute the desired result. not *, now *, and *, compose * ) and extension algebraic operators (i.e. Aggregate Functions and Operations Aggregation functiontakes a collection of values and returns a single value as a result. They accept relations as their input and yield relations as their output. Relational algebra is a procedural query language. It uses operators to perform queries. Relational algebra operations are performed recursively on a relation. An operator can be either unary or binary. Select Operation: The select operation selects tuples that satisfy a given predicate. SQL for extended relational algebra operators How Sections 5.1 – 5.2 relate to Sections 6.1 – 6.3 Week 3 CS 386/586 Fall 2012 Lois Delcambre CS386/586 Introduction to Database Systems, ©Lois Delcambre, David Maier 1999-2012 1 Relational Algebra. Relational Algebra A query language is a language in which user requests information from the database. The second is the sum of the second and third attributes of R, with the name X. Extended Operators • Powerful operators based on basic relational operators and bag semantics. One is A, the first attribute of R, not renamed. avg: average value min: minimum value max: maximum value sum: sum of values count: number of values Aggregate operationin relational algebra Eis any relational-algebra expression G 1, G 2…, G nis a list of attributes on which to group(can be empty) Relational algebra is a procedural query language, which takes instances of relations as input and yields instances of relations as output. • Sorting : convertconvert aa relationrelation intointo aa listlist ofof tuplestuples . The output of relational algebra operations is a new relation, which can be formed from one or more input relations. EXTENDED OPERATORS OF RELATIONAL ALGEBRA 219 The result’s schema has two attributes. It uses "terms" in the sense of declara-tive languages instead of basic data li-ke strings, integers, etc. Relational algebra collects instances of relations as input and gives occurrences of relations as output by using various operations. • Duplicate elimination: turn a bag into a set by eliminating duplicate tuples. : ext.. add ..by ). Extended Relational Algebra Operator Reference ... Write a SQL or Relational Algebra query that e ciently computes the new value of VIEW after rows are inserted into the indicated table (the delta query). In particular the projection and selection operators are mo-di ed and allow the projection of subterms Bags Versus SetsExtended OperatorsJoins Extended Operators in SQL and Relational Algebra T. M. Murali September 16, 2009 T. M. Murali September 16, 2009 Extended Operators in SQL and Relational Algebra For another example, t:b-a^x,c-b-+y{R) is X Y 1 1 1 1 1 1 ... -1 to -3 for missing or wrong tables or query operators Question 2. 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