What is Concat in SQL? – Function, Syntax, & More

Did you know that almost 90% of SQL developers use concatenation in their codes? Concat SQL is used to create dynamic codes and is widely popular among SQL users. It is a function in SQL that is used to join two or more strings together. 

This blog will walk you through the descriptive understanding of what is SQL concat. It will also discuss what it is used for and underline its syntax and functions with examples. Furthermore, you will also learn the advantages and disadvantages that come along with using it.

Concat Function in SQL: An Overview

In SQL, the CONCAT() function is used to connect two or more strings. It may be used in several situations, such as when you need to add a new column to a table or output a string value from a query. It can take an unlimited number of parameters and transforms null values into empty strings automatically. 

It is also important to remember that before concatenation, the CONCAT() method implicitly transforms all parameters to string types. It will return an empty string of type varchar(1) if it receives arguments with all NULL values. You can enroll yourself in an online SQL course to get a better understanding of the subject.

Concat Syntax in SQL

Now that you understand what is concat in SQL, let us move on to the syntax that is used in it:

CONCAT(string1, string2, …)

In this syntax, string1, string2,… are the strings to be concatenated.

For example, the following query would concatenate the values of the customer’s table’s first_name and last_name columns and save the result in a new column named full_name:

SELECT CONCAT(first_name, ‘ ‘, last_name) AS full_name

FROM customers;

Numeric numbers can also be concatenated using the CONCAT() function. For example, the following query would concatenate the values of the orders table’s quantity and price columns and save the result in a new column named total_cost:

SELECT CONCAT(quantity, ‘ x ‘, price) AS total_cost

FROM orders;

SQL Concat String

In SQL, you may concatenate strings using either the CONCAT() function or the + operator.

CONCAT() Function

The CONCAT() function concatenates a configurable number of string inputs into a single string. For example, the following query concatenates the student’s table’s first_name and last_name columns:

SELECT CONCAT(first_name, ‘ ‘, last_name) AS full_name

FROM students;

+ Operator

Strings can also be concatenated using the + operator. The + operator, however, will only concatenate strings; it will not concatenate strings and integers or strings and other data types. The following query, for example, will not work:

SELECT first_name + last_name AS full_name

FROM students;

Because the first_name and last_name columns are both of type varchar, this query will fail. The + operator cannot concatenate two varchar strings.

To correct this, use the CAST() method to convert one of the strings to another data type. The following query, for example, will work:

SELECT CAST(first_name AS varchar(255)) + last_name AS full_name

FROM students;

This query will convert the first_name column to the same data type as the last_name column, varchar(255). The + operator will then be able to concatenate the two strings.

It is entirely up to you the method you use to concatenate strings. The CONCAT() function is more straightforward and easier to comprehend than the + operator.

How To Concat Two Columns In SQL

The CONCAT() function in SQL is used to concatenate two columns. CONCAT() accepts two or more inputs and returns a concatenated string. The following query, for example, would concatenate the first and last name fields in the customer’s table: 

SELECT CONCAT(first_name, ‘ ‘, last_name) AS full_name

FROM customers;

This would result in the creation of a new column named full_name, which would include the concatenation of the first and last name columns.

In SQL, you can additionally concatenate strings by using the + operator. The + operator is more versatile than the CONCAT() function in that it can concatenate strings of multiple data kinds. The following query, for example, would concatenate the first name and age fields in the customer’s table:

SELECT first_name + ‘ is ‘ + age AS full_name

FROM customers;

This would result in the creation of a new column named full_name, which would include the concatenation of the first name and age fields.

In SQL, you can concatenate strings using the CONCAT() function or the + operator. CONCAT() is more explicit, whereas the + operator is more flexible. The approach you choose will be determined by your requirements.

Concat Function With Null Value

NULL is a special pointer in SQL Server that specifies a value that is undefined or is not present. When a NULL value is sent as an argument to the CONCAT function, it is transformed into an empty string. 

An example:

SELECT CONCAT(‘Hello ‘, Name, ‘!’) AS Greeting

FROM Customers

WHERE Name IS NOT NULL;

This query will provide a list of greetings for all customers whose names do not contain the word NULL. For example, suppose the Customers table has the following information:

| Name |

|—|—|

| John Doe |

| Jane Doe |

| NULL |

The result would be:

| Greeting |

|—|—|

| Hello John Doe! |

| Hello Jane Doe! |

| NULL |

As you can observe, if the Name column is empty, the CONCAT method will return NULL.

Uses Of Concat Function In SQL

The CONCAT function is a powerful tool that may be used to tackle a wide range of SQL problems. You may use it to increase the efficiency and readability of your queries if you understand how it works. The following are some of its uses:

• To generate a unique identifier for a table row.
• To develop a more understandable data representation.
• To construct dynamic SQL statements.
• To generate personalized error messages.

Advantages And Disadvantages Of CONCAT Function

The following points explain the advantages and disadvantages:

Advantages

• The CONCAT function is really simple to use. CONCAT(string1, string2) is the syntax, where string1 and string2 are the strings to be concatenated.
• CONCAT is a versatile function that may be utilized in several circumstances. For example, you may use it to combine a customer’s first and last name, or the product name and quantity of a product in an order.
• CONCAT is a very efficient function. It requires no extra processing and may be applied to very big datasets.

Disadvantages

• The CONCAT function can be slow with large datasets. This is because it must process each string independently.
• Debugging the CONCAT function might be tough. This is because it might be difficult to pinpoint the source of a mistake when numerous strings are involved.
• The CONCAT function is not particularly adaptable. It can only join strings together. It can’t be used to do things like convert a string to a number or execute a mathematical operation on two strings.

Conclusion

Concat in SQL is used to create dynamic codes and is widely popular among SQL users. It is versatile and quite simple to use. However, you must have adequate knowledge about it before you get to use it.