“That query’s not sargable” says one developer to another.
“I know it’s not sargable… would you love it more if it had sargability?” replies the other developer.
“What does sargable mean?” you wonder in silence.
Database Concepts
What is User-Defined Integrity?
Maintaining data integrity is critical for ensuring the accuracy, consistency, and reliability of data inside a relational database. Among the various strategies to enforce data integrity, user-defined integrity plays a significant role, especially in customized applications and systems where standard integrity constraints may not suffice.
This article explores the concept of user-defined integrity, its importance, how it is implemented, and scenarios where it can become essential.
What is a One-To-One Relationship?
In relational databases, a one-to-one relationship is a relationship between two tables where each record in the first table corresponds to one and only one record in the second table, and vice versa.
This kind of relationship is less common compared to other relationship types, but it can be useful in certain scenarios. The one-to-many and many-to-many relationships are much more common than the one-to-one relationship in SQL.
Understanding the NOT NULL Constraint in SQL
In SQL, constraints are essential for maintaining data integrity and ensuring the accuracy and reliability of the data stored within a database. One of the most commonly used constraints in SQL databases is the NOT NULL constraint.
In this article, I provide a quick overview of the NOT NULL constraint, its purpose, syntax, usage, and practical examples.
Understanding the DEFAULT Constraint in SQL: A Complete Guide
The DEFAULT constraint is a nifty little feature in SQL databases that simplifies data management by assigning default values to columns in a table. This can help us maintain data integrity in our databases.
Let’s take a look at the DEFAULT constraint.
Understanding the “Key Lookup” in SQL Server
When looking through the execution plan in SQL Server, you may occasionally see “key lookup” glaring back at you.
If you find this happening a lot, and on frequently run queries, then you might want to do something about it.
What is a One-To-Many Relationship?
When working with relational databases, we tend to create a lot of relationships between tables. But not all relationships are created equal – there are different types of relationships. The one-to-many relationship is probably the most common type of relationship in relational database design.
A one-to-many relationship is a type of association between two tables where a record in one table (the “one” side) can be related to multiple records in another table (the “many” side). For example, in an e-commerce database, a single customer can place many orders. In this scenario, the Customers table would have a one-to-many relationship with the Orders table.
What is a Many-To-Many Relationship?
In SQL, a many-to-many relationship occurs when multiple records in one table can be associated with multiple records in another table.
To represent this type of relationship, a third table—often referred to as a “junction table” or “associative entity”—is used. This junction table typically contains foreign keys that reference the primary keys of the two related tables, allowing for the connection between multiple records.
Understanding the RID in SQL Server
You may have seen the term “RID lookup” when reading about heap tables, or perhaps when viewing the query plan for a query against a heap in SQL Server.
But what exactly is a RID lookup? And what exactly is a RID?
Let’s find out.
Compound Keys Explained
In SQL databases, a compound key is a type of primary key that consists of two or more columns combined to uniquely identify each row in a table. The key columns are used together as a single unit to ensure uniqueness.
Some within the SQL community define compound keys as composite primary keys comprising of foreign keys from other tables, so there doesn’t seem to be an agreed consensus on the precise definition.
With that in mind, let’s explore these definitions of compound keys.