Do you want to know how to concatenate two columns in SQL? Well, after reading this article, you will be able to perform SQL concatenation. Are you ready to dive in?
You might have heard about concatenation in various programming languages like C++, Python, and more. Did you know that in SQL, you can also perform concatenation using different methods? Well, we will discuss each method in this article.
Let us get started with the topic at hand without any further discussion!
Summary Of The Article:
The process of concatenation in SQL means to join together two different strings.
This can be done using different functions provided by SQL or by using different operators.
Concatenation can be used in various examples, for example, joining the first and last names of people to form the complete name.
We can, thus, use this effective method to enhance the functionality of SQL and handle the data stored in our database systems.
What Is SQL Concatenation?
Concatenation in SQL simply means to combine multiple strings, values, or columns into a single column. There are various ways to concatenate values in SQL depending on which type of database system you are using.
SQL Concatenation is an important concept as it helps to enhance data management and presentation. Further, it increases accuracy and flexibility by giving us the means to customize data representation according to certain conditions.
As we said before, we can perform concatenation in SQL using different methods and operators. Let us see what these methods are:
The Two Ways To Perform Concatenation in SQL:
Below are the ways that can be used for concatenating in SQL. Have a look a these below:
Using CONCAT function
Using Concatenation operator
We will discuss both of these ways in this article with the help of examples. But for that, we will have to create a database.
How to create a database table in SQL?
Select the database system of your choice, like MySQL, and get started for some practice! Let us create a table called Person and add some values to it. The process is given below.
Create a table and define data types
CREATE TABLE Person(
id int,
firstname varchar(10),
lastname varchar(10),
city varchar(14)
);
The columns in the above example have int and varchar types for the values.
Add values to the table columns:
INSERT INTO Person VALUES
(1, 'Abby', 'Hart', 'Paris'),
(2, 'Harry', 'Styles', 'London'),
(3, 'Taylor', 'Swift', 'Kansas');
The resultant table is given below. We will use this table as our example throughout the article.
How To Perform SQL Concatenation On Two Columns?
If you are wondering ‘How do I concatenate two columns of data in SQL?’ We got you!
Just like we concatenate two or more strings, we can also concatenate multiple columns in SQL. Here, we will use the CONCAT function and the || operator to do our task in the table given above. Are you ready to learn? Let’s start!
Concatenate Two Columns Using CONCAT Function:
The CONCAT function works in two ways. We can either concatenate two values into an existing column or add them into a new column. Here, we will see how to do both and write SQL queries for the same.
CONCAT function in SQL takes the column names we want to join as parameters and returns a column with the resulting values after concatenation. The syntax for using the CONCAT function is given below.
CONCAT(column1, column2) AS columnname;
Let us now concatenate the first and last names column using the CONCAT function without using or replacing the existing column. The query to do this is given below. Have a look at this SQL statement.
SELECT *, CONCAT(firstname, lastname) AS fullname FROM Person;
The query result for the above query is given below. You will notice that a new column named full name is added at the end.
Now, let us see how to use the CONCAT function by replacing the existing column. Here, we will use the REPLACE function to replace the ‘firstname’ column and space as a delimiter. Have a look at the example query below.
UPDATE Person
SET firstname = REPLACE(firstname, firstname, CONCAT(firstname,' ', lastname));
In the output below, we can see that the first name column, now has the concatenated values and that the previous values in this column are successfully concatenated into a single string.
In case, you’re facing difficulties in understanding the output tables, then you ask for SQL homework help from experts online.
Concatenate Two Columns Using Concatenation Operator:
We saw how to use the CONCAT function to concatenate firstname and lastname column values in our query examples. Now, we will use the || or operator to do the same. The query results will show the concatenation of different columns.
The syntax to use the || operator is given below:
column1 || column2
Again, we will concatenate ‘firstname’ column and the ‘lastname’ column in the following example. The SQL query is given below.
SELECT
first name || lastname
FROM Person;
The result for this query is given below.
There are different SQL databases like MySQL, SQLite, Oracle, MS SQL Server, and more. Concatenating columns depends on the type of database you are using. In SQL Server, you can use the + operator for concatenation.
How To Concatenate Columns Using + Operator in SQL Server?
Another method to concatenate strings is using the plus sign or the plus symbol. This is known as the + operator in SQL Server and can be used for concatenating two or more columns in a table.
Let us use the same table ‘Person’ as the example. We will concatenate the city and lastname columns and store the concatenated string in a column named passkey. Look at the syntax of query example below to know how it works.
SELECT id, city + ' ' + lastname AS passkey FROM Person;
When we run the above query in SQL Server, we will see that the + operator concatenated the string city with the string lastname with a space in between as we have used the space as a delimiter.
Now that we know how concatenation works, we can perform it on all the columns we desire. But, what if there exist some null values in your data? Let us dive deeper and see how to work with data containing null values with the help of examples.
Handling Null Values At Time Of Concatenation
When your data contains null values, concatenating may lead to an error. To avoid such situations we can either make use of the ISNULL function or COALESCE function to handle a missing or null value in your data.
Here, we will see how to use the COALESCE function in your standard SQL query for handling a NULL value. Be mindful that a NULL value is not an empty string. They are different from each other.
So, what does this function do? COALESCE returns a non-null value whenever any NULL value is encountered. For example, let us have another row in our database table where the ‘firstname’ field has a null value instead of a string value.
Concatenating two strings is now not possible, therefore, we will return id in this case as a substitute. The query is given below.
SELECT id,COALESCE(firstname || lastname, id) AS fullname, city FROM Person;
In the resulting output, we can see that the last row value for the full name says 4 instead of any other name or an empty string. This is done using COALESCE.
Isn’t it a game-changer? When you learn how to handle null or missing values, your queries become more effective.
Conclusion:
Now, you can gain hands-on experience for concatenation in the SQL database system of your choice. Remember that different database management systems may use different operators or functions for this purpose. Like, in SQL server, you can use the + operator efficiently, but in MySQL, using the Concat function is a better choice.
I hope that you are now clear about how to concatenate two columns in SQL. Well, with a little more practice, you even join two or more columns easily! So, what are you waiting for? Practice now!
We understand that DBMS can be a difficult concept as it involves coding. Then you can ask for DBMS help online from CodingZap experts.
Key Takeaways:
You can join or combine one string with another in SQL using the process of concatenation.
This concept is beneficial and has various use cases as well. Not only does it help to present our data in a better way but also makes data retrieving using queries easy.
In systems like MySQL, one way to perform this can be by using the CONCAT function. While, in SQL server, you can also use the + operator along with the CONCAT function for the same.
Another thing to keep in mind while performing concatenation is to make sure that you handle null values efficiently. Handling Null values will prevent errors and give you better results.
