# Questions tagged [relational-algebra]

the study of relations (i.e., database tables) and relational operators (join, selection, projection, etc.) as a kind of algebraic structure.

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### Algorithm for segmenting input query into query/join tree

Wondering what algorithms look like for implementing a complex JOIN query handler. Taking a look at this paper Building Query Compilers they talk about Query Graphs ...
21 views

### Optional filters in relational database

I'm trying to create a procedure in MySQL/MariaDB with optional filters for each participating table. Assuming the tables are $A, B, C, \ldots$, each table may or may not be filtered, and the result ...
130 views

### Two related partial order relations

We will consider a set whose elements I call "precedences". Precedences are related by two relations: "is subclass of" and "higher than", which are specified by some pairs (given on algorithm input) ...
208 views

### Using cross-products with relational algebra

I have some questions about something that I'm working on in an assignment for my database class. Here is the schema for the questions I'm working on, so that you know what to refer to: ...
26 views

### Is it possible to convert any relational algebra expression into a relational calculus expression?

Let's for the sake of simplicity only focus on tuple relational calculus. Every relational algebra query can be broken down into the 5 atomic operations - projection, selection, set union, set ...
24 views

### constant relation in the base case of relational algebra

in the base case of the inductive definition of the operations of the relational algebra there is also the so called "constant relation" (as for example found in the definition here https://...
19 views

### Which of the query approaches are more efficient?

There are two relations, registered(participant,topic) and fee(participant,amount). The primary key for registered is (participant, topic) and the primary key for fee is participant. The premise is ...
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### Is Neo4J computationally equivalent to relational algebra

I am wondering whether Neo4j and the associated Cypher query language is computationally equivalent to relational algebra? Any ideas or papers on that topic?
343 views

### how to get rows with more than 1 appearance of a specific column in relational algebra

I have a table like this: ...
66 views