Top "Relational-database" questions

A relational database is a database consisting of relation variables (which are also called *relvars*, *R-tables* or just *tables*). The definition, manipulation and integrity rules of relational databases are based on relational operations equivalent to or similar to the Relational Algebra and Calculus.

How to create relationships in MySQL

In class, we are all 'studying' databases, and everyone is using Access. Bored with this, I am trying to do …

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Laravel - Eloquent "Has", "With", "WhereHas" - What do they mean?

I've found the concept and meaning behind these methods to be a little confusing, is it possible for somebody to …

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What are the options for storing hierarchical data in a relational database?

Good Overviews Generally speaking, you're making a decision between fast read times (for example, nested set) or fast write times (…

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Difference between 3NF and BCNF in simple terms (must be able to explain to an 8-year old)

I have read the quote : data depends on the key [1NF], the whole key [2NF] and nothing but the key [3…

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Difference between one-to-many and many-to-one relationship

What is the real difference between one-to-many and many-to-one relationship? It is only reversed, kind of? I can't find any …

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What is the difference between a candidate key and a primary key?

Is it that a primary key is the selected candidate key chosen for a given table?

sql relational-database
Why use multiple columns as primary keys (composite primary key)

This example is taken from w3schools. CREATE TABLE Persons ( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName …

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Does the join order matter in SQL?

Disregarding performance, will I get the same result from query A and B below? How about C and D? -- …

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How to perform a LEFT JOIN in SQL Server between two SELECT statements?

I have two SELECT statements in SQL Server like these: (SELECT [UserID] FROM [User]) (SELECT [TailUser], [Weight] FROM [Edge] WHERE […

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