In PostgreSQL, both UNIQUE indexes and UNIQUE constraints can be used to enforce uniqueness on columns.
So you may be wondering; if that’s true, why have both? And are there any circumstances that we should choose one over the other?
Let’s find out.
Continue readingStructured Query Language (SQL) is the backbone of relational database management systems (RDBMSs), enabling users to query, manipulate, and define data. One of the most fundamental concepts in SQL, and one that all SQL developers should understand, is the data type.
Whenever we create a column in SQL, we must define its data type. Similarly, when we create a variable, we define its data type.
So, why is the data type so important? Let’s find out.
Continue readingWhen using PostgreSQL’s psql command line tool, we can use the \dt command to get a list of tables. This meta-command can display all tables, or just tables that match certain patterns. Below is an overview of how \dt works, its options, and examples of its various uses.
A junction table, also known as an associative table or a bridge table, is a table used to manage many-to-many relationships between two other tables in a relational database.
In SQL, many-to-many relationships cannot be directly implemented using just two tables because each table’s foreign key can only relate to one other table’s primary key. Instead, a junction table is created to “link” the two tables together.
Continue readingMaintaining the reliability, accuracy, and consistency of data is paramount when dealing with databases. One important factor that plays a huge role in ensuring these qualities is the concept of physical integrity.
While much attention is given to logical integrity—ensuring the data follows the rules of the schema and maintains meaningful relationships—physical integrity is equally important. It deals with the actual storage of data and the correct functioning of the hardware and software systems that store and manage this data.
This article delves into what physical integrity is in the context of database management, why it is important, how it can be compromised, as well as best practices for maintaining it.
Continue readingIn SQL Server, foreign keys are essential for maintaining referential integrity between tables. When creating foreign keys, we have a number options available to us when it comes to defining what should happen in the event that the related data in the parent table changes. One such option is ON UPDATE SET DEFAULT.
This article will explain what this option does, provide an example of its usage, and offer a practical scenario where this feature can be useful.
Continue readingIn PostgreSQL, indexes on expressions (also known as “functional indexes”) allow you to create an index not just on a column but on the result of an expression or function applied to a column (or multiple columns). This can significantly improve query performance when the same expression is used frequently in queries, especially for complex calculations or transformations.
Continue readingPrepared statements are a feature in PostgreSQL that can improve performance and security when executing repetitive SQL queries.
By creating a prepared statement, the server can parse and plan the query once and reuse it multiple times, leading to faster execution. Prepared statements also help in preventing SQL injection attacks by safely handling user input.
In this article, we’ll explore prepared statements in PostgreSQL, discuss how to create and use them, and cover other important considerations such as query planning and cleaning up statements.
Continue readingAdding indexes to a table is a well established practice for speeding up regular queries in relational databases such as PostgreSQL. While they can do wonders for query performance, indexes can also take up a lot of disk space.
Today we’re going to be looking at a particular type of index that can help reduce the impact on disk space, and query performance – the partial index.
Continue readingIndexes can play a crucial role in optimizing SQL query performance. A well designed index can help a query perform much faster than it otherwise might. While there are many types of indexes, two common index types are clustered and nonclustered indexes.
Understanding the difference between clustered and nonclustered indexes can have a significant impact on our database design and query optimization strategies.
In this article, we’ll take a look at clustered and nonclustered indexes as implemented in SQL Server, explore their characteristics, and examine when to use each type.
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