There are various key types in SQL, each with their own characteristics. Some of these can be enforced with a constraint of one kind or another. Others are not necessarily enforced with a constraint, but are more of an abstract notion, albeit, an important one. These key types consist of one or more columns with certain characteristics that qualify it as the particular key.
One such key type is the superkey.
In relational databases, a foreign key is typically a field that is linked to another table‘s primary key field in a relationship between two tables.
However, there’s also a type of foreign key we call the self-referencing foreign key. The self-referencing foreign key refers to a field within the same table, creating a relationship between rows in the same table.
In SQL databases, triggers can play a significant role in automating responses to specific events within a database. Whether we’re dealing with data validation, logging changes, or enforcing business rules, SQL triggers can be a handy tool to ensure that certain actions are taken automatically when certain conditions are met.
This article covers what SQL triggers are, how they work, and provides an example to illustrate their use.
When writing queries in SQL, we sometimes need to summarize data based on specific criteria. Fortunately SQL makes this easy to achieve with the GROUP BY and HAVING clauses. These two clauses allow us to aggregate data and filter the results based on group conditions.
More specifically, GROUP BY allows us to group the results, and HAVING is an optional clause that we can use to filter the results based on certain conditions.
Below is an example of where we can use these two clauses to aggregate data and filter it based on certain criteria.
In relational database design, the concept of a “key” is fundamental. Keys are essential for uniquely identifying records in a table, ensuring data integrity, and facilitating efficient data retrieval. Among the different types of keys used in SQL, the natural key is one that often sparks discussion among database designers, especially when compared with the surrogate key.
Let’s explore the concept of a natural key, its advantages and disadvantages, and look at a practical example to illustrate its use.
While the primary key is almost certainly the most discussed key in SQL, there are other types of keys that we shouldn’t forget. One such key is the alternate key.
In this article, we’ll look at the concept of the alternate key in SQL.
There are many different “key” types in SQL. We have the primary key, the foreign key, and even the unique key.
But have you heard about the candidate key?
One of the core principles that ensure data integrity in relational database management systems (RDBMSs) is atomicity. When dealing with SQL, understanding what “atomicity” and “atomic” means can help you design more reliable and robust databases.
Atomicity is a key concept that underpins how SQL transactions operate, ensuring that either all steps in a transaction are completed successfully, or none are. This article looks at the meaning of atomic in SQL, its importance, and how it fits into the broader context of database management.
The SQL CASE statement is a handy tool that allows us to add conditional logic to our queries. It’s particularly useful when we need to categorize or transform data based on multiple conditions.
In this article, we’ll explore how to use the CASE statement with multiple conditions, providing simple examples that should work across most major relational database management systems (RDBMSs).
