Understanding Concatenate in SQL Server

Dear Dev, if you’re a database developer or administrator, you must be acquainted with SQL Server. It’s one of the most widely used relational database management systems. In SQL Server, concatenation is a common requirement for combining two or more strings into one. This is where the CONCAT function comes into play. In this article, we will discuss the CONCAT function in detail and its usage in SQL Server.

What is Concatenation?

Concatenation is the process of combining two or more strings into one. This is one of the most common requirements in SQL Server development. You may have to concatenate two or more strings to create a full name or address for a customer. This is where the CONCAT function comes into play.

How to Use the CONCAT Function?

The CONCAT function in SQL Server is used to concatenate two or more strings into one. The syntax of the CONCAT function is as follows:

Parameter	Description
string1, string2, … stringN	The strings to concatenate

Working with Concatenation in SQL Server

There are several ways to concatenate strings in SQL Server. In this section, we will discuss some of the most common methods.

Using the + Operator

The + operator is used to concatenate two or more strings in SQL Server. The syntax is as follows:

SELECT FirstName + ‘ ‘ + LastName AS FullName FROM Customers;

This will return a new column named FullName, which is the concatenation of the FirstName and LastName columns.

Using the CONCAT Function

The CONCAT function can also be used to concatenate strings in SQL Server. The syntax is as follows:

SELECT CONCAT(FirstName, ‘ ‘, LastName) AS FullName FROM Customers;

This will return the same result as the previous example.

Concatenation with NULL Values

When concatenating strings that may contain NULL values, the CONCAT function and the + operator behave differently.

Using the + Operator with NULL Values

If any of the strings being concatenated is NULL, the result is NULL.

SELECT FirstName + ‘ ‘ + MiddleName + ‘ ‘ + LastName AS FullName FROM Customers;

If the MiddleName column contains NULL, the result of the concatenation will be NULL.

Using the CONCAT Function with NULL Values

If any of the strings being concatenated is NULL, the result is still a string.

SELECT CONCAT(FirstName, ‘ ‘, MiddleName, ‘ ‘, LastName) AS FullName FROM Customers;

If the MiddleName column contains NULL, the result of the concatenation will be FirstName LastName.

FAQ

What is the maximum number of strings that can be concatenated using the CONCAT function?

There is no limit to the number of strings that can be concatenated using the CONCAT function.

Can I use the CONCAT function in a WHERE clause?

Yes, the CONCAT function can be used in a WHERE clause.

SELECT * FROM Customers WHERE CONCAT(FirstName, ‘ ‘, LastName) = ‘John Doe’;

This will return all customers whose full name is John Doe.

Can I use variables with the CONCAT function?

Yes, variables can be used with the CONCAT function.

DECLARE @FirstName varchar(50) = ‘John’; DECLARE @LastName varchar(50) = ‘Doe’; SELECT CONCAT(@FirstName, ‘ ‘, @LastName) AS FullName;

This will return the full name John Doe.