Reading Time: 3 minutes There is an interesting factoid you should know when it comes to working with foreign key constraints in SQL Server. Normally, foreign key constraints are linked to a Primary Key column in a parent table Take a look at the following Books and BookSales tables: CREATE TABLE Books ( BookID Continue Reading
Constraints
Difference between unique constraints and primary key constraints: Answered with examples
Reading Time: 4 minutes A primary key constraint and a unique constraint are both meant to enforce uniqueness in column(s). Since that’s true, it begs the question: What’s the difference? In this very brief tutorial, we’ll discuss the two main differences between primary key constraints and unique constraints. Difference # 1: Primary key constraints Continue Reading
Why can’t I add a foreign key constraint? ANSWERED!
Reading Time: 4 minutes When attempting to create a foreign key constraint on a table, you may receive an error message very similar to the following: The ALTER TABLE statement conflicted with the FOREIGN KEY constraint “constraint_name”. The conflict occurred in database “DatabaseName”, table “TableName”, column ‘ColumnName’. This may be happening because you are Continue Reading
How to disable a Foreign Key Constraint: Run this ONE simple statement!
Reading Time: 3 minutes Foreign key constraints are an excellent way to preserve the referential integrity of the data in your database. If you’re new to SQL Server and don’t fully understand what a foreign key is or how they work, make sure you check out the full beginner-friendly tutorial first to learn everything Continue Reading
Do you know this IMPORTANT RULE about Foreign Key Constraints?
Reading Time: 5 minutes Foreign Key Constraints in Microsoft SQL Server are excellent for preserving the integrity of our data. We use a foreign key constraint to basically establish a parent-child relationship between two tables. A foreign key constraint will enforce that a value must first exist in the parent table before it can Continue Reading
How to drop a constraint in SQL Server: Explained with Examples
Reading Time: 4 minutes It’s very easy to drop a constraint on a column in a table. This is something you might need to do if you find yourself needing to drop the column, for example. SQL Server simply will not let you drop a column if that column has any kind of constraint Continue Reading
How to find foreign key references in SQL Server: Just run this one query!
Reading Time: 4 minutes SQL Server foreign key constraints are one of the most useful tools available to us for maintaining the integrity of our data. If you want to find all the foreign key references in your database, there is a very simple query you can run. Just query the sys.foreign_keys and sys.foreign_key_columns Continue Reading
SQL Server Default Constraint: A Guide for Beginners
Reading Time: 6 minutes In Microsoft SQL Server, one of the things we should always keep in mind is the integrity of our data. One of the best ways to maintain data integrity is to introduce constraints into our tables. Constraints are a great way to restrict the data that can be inserted into Continue Reading
SQL Server Check Constraint: Full Beginner-Friendly Tutorial
Reading Time: 11 minutes When working with SQL Server databases, one of the most important things we should always keep in mind is the integrity of our data. We should do our best to make sure the data in our database is valid. One of the best ways we can accomplish this is through Continue Reading
What is a Candidate Key in SQL Server? Answered!
Reading Time: 7 minutes There are many different keys in SQL Server that are important to understand. You might have heard the term “Candidate Key” before, but maybe you aren’t exactly sure what that means. Maybe you know a thing or two about Primary Keys and Foreign Keys, but you’re not sure what the term “Candidate Continue Reading