find the names of students who registered at least one course in semester relational algebra

Is it possible to do this query in basic relational algebra?

Strictly speaking, this query cannot be done in the basic (original) relational algebra. We have to use the AGGREGATE FUNCTION operation with the COUNT aggregate function.

What are the basic operators in relational algebra?

Relational Algebra • Domain: set of relations • Basic operators: select, project, union, set difference, Cartesian product • Derived operators: set intersection, division, join • Procedural: Relational expression specifies query by describing an algorithm (the sequence in which operators are applied) for determining the result of an expression 3 5

How to find all professors who taught at least two courses?

Find Ids of all professors who taught at least two courses in the same semester: SELECT T1.ProfId FROM Teaching T1, Teaching T2 WHERE T1.ProfId = T2.ProfId AND T1.Semester = T2.Semester AND T1.CrsCode <> T2.CrsCode Tuple variables are essential in this query! Equivalent to:

Are relational algebra expressions procedural or procedural?

• Relational algebra expressions are procedural. Which of the two equivalent expressions is more easily evaluated? 32 Self-join Queries Find Ids of all professors who taught at least two courses in the same semester:

How do you get names and marks of the top 3 students?

SELECT statement is used to get name and marks of top three students.SQL query is. SELECT Name, Marks FROM Student s1 where 3 <= (SELECT COUNT(*) FROM Students s2 WHERE s1.marks = s2.marks)SQL (Structured Query Language) ... Functions of SQL (Structured Query Language)

How do I count the number of students in SQL?

SELECT COUNT(column_name) counts the non-null values of column in the table. The total number of STU_DEPT values in above table are 7 but one of them is null. Since count(column_name) counts non-null values of the given column, thus the output is 6.

How do you represent a count in relational algebra?

3 Answersevery statement by its table/relation.every AND of table/relation by ⋈ (natural join)every OR of table/relation (which must have the same columns/attributes) by ∪ (union)every AND NOT (which must have the same columns/attributes) by \ (difference)every AND comparison by σ comparison (select/restrict)More items...•

What is relational algebra * Your answer?

Relational Algebra is procedural query language, which takes Relation as input and generate relation as output. Relational algebra mainly provides theoretical foundation for relational databases and SQL. Projection is used to project required column data from a relation.

How do I find the number of employees in SQL?

SELECT department, COUNT(*) AS "Number of employees" FROM employees WHERE state = 'CA' GROUP BY department; Because you have listed one column in your SELECT statement that is not encapsulated in the COUNT function, you must use a GROUP BY clause. The department field must, therefore, be listed in the GROUP BY section.

How can I get total number of employees in SQL?

You can use the COUNT function in the SELECT statement to get the number of employees, the number of employees in each department, the number of employees who hold a specific job, etc. The result of the COUNT function depends on the argument that you pass to it.

How do you solve a relational algebra query?

17:1121:39Relational Algebra Queries (Part 1) - YouTubeYouTubeStart of suggested clipEnd of suggested clipHere we see that there are only two tuples that satisfy the given join condition therefore theMoreHere we see that there are only two tuples that satisfy the given join condition therefore the result of this join condition will be a combination of these matched tuples.

What is relational algebra explain with example?

Relational algebra is a procedural query language, which takes instances of relations as input and yields instances of relations as output. It uses operators to perform queries. An operator can be either unary or binary. They accept relations as their input and yield relations as their output.

How do you write relational algebra in Word?

0:241:18How to Use Relation Symbols on Microsoft Word : MS Word & ExcelYouTubeStart of suggested clipEnd of suggested clipRight in the document where you'd like to insert it and then if you just simply click on theMoreRight in the document where you'd like to insert it and then if you just simply click on the relation symbol. It will insert it for you likewise with the other relation.

What is relational algebra state and explain any five relational algebra operations with proper example?

SummaryOperation(Symbols)PurposeIntersection(∩)Intersection defines a relation consisting of a set of all tuple that are in both A and B.Cartesian Product(X)Cartesian operation is helpful to merge columns from two relations.Inner JoinInner join, includes only those tuples that satisfy the matching criteria.11 more rows•Apr 23, 2022

Which of the following is relational algebra operations Mcq?

Which of the following is a fundamental operation in relational algebra? Explanation: The fundamental operations are select, project, union, set difference, Cartesian product, and rename. 3.

Where is relational algebra used?

The main application of relational algebra is to provide a theoretical foundation for relational databases, particularly query languages for such databases, chief among which is SQL. Relational databases store tabular data represented as relations.