Concatenate Strings in an SQL Query With Examples

Understanding how to merge or join strings together in SQL is crucial for handling data effectively. This is especially handy when you’re creating SQL queries, helping you combine info from different columns, make meaningful labels, and get data ready for analysis. In this guide, we’ll tell you how to write an SQL query to concatenate strings using different ways such as the plus (+) operator, CONCAT() function, || concatenation operator (Oracle, MySQL), and advanced string functions like SUBSTRING() and INSTR().

Must Read: MySQL CONCAT to Concatenate Strings

How to Write SQL Queries to Concatenate Strings

There are multiple ways you can form a SQL query to concatenate strings. However, firstly, we’ll see why is it useful to combine strings in SQL.

Multiple Use Cases

Concatenating strings in SQL queries does more than just join names together. Think about these everyday situations:

• Creating full names: Combining first and last names for easier recognition.
• Building file paths: Making dynamic file paths by putting together directory names and filenames.
• Generating URLs: Merging base URLs with dynamic details for API calls or web scraping.
• Formatting data: Adding specific symbols or characters for cleaner data display or analysis.
• Extracting data: Combining string parts based on specific patterns or separators.

Also Check: String Concatenation in Python

Methods for Concatenate Strings in SQL

SQL gives us different methods to combine strings, each with its own strengths. Let’s look at some of the most common ones:

The Plus (+) Operator

The plus (+) operator in SQL is like a basic tool for adding strings together. It’s simple, but we need to be a bit careful with it. Let’s look at more examples:

1. Combining Address Lines:

   SELECT street_number + ' ' + street_name AS full_address
   FROM addresses;

Here, the plus operator adds the street number, a space, and the street name, forming a neat ‘full_address’ column.

2. Building Invoice IDs:

   SELECT 'INV-' + invoice_number AS invoice_id
   FROM invoices;

Using the plus operator, we add a prefix ‘INV-‘ to the ‘invoice_number’ to create unique ‘invoice_id’ values.

3. Creating Event Titles:

   SELECT event_name + ' on ' + event_date AS event_title
   FROM events;

The plus operator effortlessly combines ‘event_name’, the phrase ‘on’, and ‘event_date’ for a descriptive ‘event_title’.

While the plus operator is a straightforward way to merge strings, we need to be mindful of its nuances, especially when dealing with NULL values and different data types. It’s a quick tool for simple tasks but may have some limitations.

Example:

SELECT first_name + ' ' + last_name AS fullname
FROM customers;

Here, the + operator joins the first_name and last_name columns, creating a new column labeled as full name.

The CONCAT() Function

The CONCAT() function in SQL is your go-to wizard for effortlessly combining text. Think of it as a tool that can seamlessly merge different bits of information. Let’s explore more examples to see its simplicity in action:

Also Refer: Pandas to Merge CSV Files in Python

1. Creating Full Names:

   SELECT CONCAT(first_name, ' ', last_name) AS full_name
   FROM employees;

Here, CONCAT() joins the first name, a space, and the last name to create a user-friendly ‘full_name’ column.

2. Building Email Addresses:

   SELECT CONCAT(username, '@company.com') AS email
   FROM users;

This example forms email addresses by merging the ‘username’ with a fixed domain.

3. Combining Product Details:

   SELECT CONCAT(product_name, ' - ', category) AS product_details
   FROM products;

CONCAT() effortlessly combines ‘product_name’, a dash, and ‘category’ for a comprehensive ‘product_details’ column.

In these instances, CONCAT() acts as a handy assistant, seamlessly bringing together different text elements to enhance data representation. It’s the go-to solution for making your data look organized and polished!

The || Combining Operator (Oracle, MySQL)

The double pipe (||) combining operator in SQL is a bit like the plus operator, but it’s more particular about things like data types and dealing with NULL values. Let’s explore more scenarios:

1. Crafting Message Previews:

   SELECT 'Preview: ' || message_body AS preview_text
   FROM messages;

Here, the || operator adds the phrase ‘Preview: ‘ to the ‘message_body’, creating an informative ‘preview_text’.

2. Forming Book Titles:

   SELECT book_title || ' by ' || author_name AS full_title
   FROM books;

Using the || operator, we seamlessly combine ‘book_title’, the phrase ‘by’, and ‘author_name’ for a comprehensive ‘full_title’.

3. Building URL Links:

   SELECT 'https://' || website_domain || '/home' AS homepage_link
   FROM websites;

The || operator constructs a complete URL link by adding 'https://', ‘website_domain’, and ‘/home’.

While the || operator is similar to the plus operator, it has its own set of rules. It’s more specific about the types of data it can handle and how it deals with NULL values. This makes it a reliable tool for certain concatenation tasks, offering precision in string combining.

Using String Functions

In SQL, there’s a toolbox of powerful functions like SUBSTRING(), INSTR(), REPLACE(), LPAD(), and RPAD() designed for intricate merging tasks. Let’s find out how to use these:

1. Extracting Area Codes:

   SELECT SUBSTRING(phone_number, 1, 3) AS area_code
   FROM contacts;

The SUBSTRING() function captures the first three characters of ‘phone_number’, creating a dedicated ‘area_code’ column.

2. Finding Keywords:

   SELECT INSTR(description, 'SQL') AS keyword_position
   FROM articles;

INSTR() identifies the position of ‘SQL’ within the ‘description’, helping us locate key information.

3. Fixing Typos:

   SELECT REPLACE(product_name, 'Mngr', 'Manager') AS corrected_name
   FROM products;

The REPLACE() function corrects ‘Mngr’ to ‘Manager’ in the ‘product_name’, producing a polished ‘corrected_name’.

4. Padding ZIP Codes:

   SELECT LPAD(zip_code, 5, '0') AS padded_zip
   FROM addresses;

Using LPAD(), we add zeros on the left of ‘zip_code’ to ensure a consistent length, creating a ‘padded_zip’ column.

Using CASE Statements

In SQL, CASE statements act like smart decision-makers. It helps form SQL queries to concatenate strings using conditions. Let’s look at some practical examples:

1. Product Availability:

   SELECT product_name, 
          CASE WHEN stock_quant > 0 THEN 'In Stock'
               ELSE 'Out of Stock'
          END AS stock_status
   FROM inventory;

Here, the CASE statement labels products as ‘In Stock’ or ‘Out of Stock’ based on their availability.

2. Task Priority Levels:

   SELECT task_name, 
          CASE WHEN prio = 'High' THEN 'Urgent'
               WHEN prio = 'Medium' THEN 'Moderate'
               ELSE 'Low'
          END AS prio_level
   FROM tasks;

This CASE statement assigns priority levels (‘Urgent’, ‘Moderate’, or ‘Low’) to tasks based on their priority.

3. Customer Satisfaction Ratings:

   SELECT cust_name, 
          CASE WHEN satisfaction_score >= 4 THEN 'Happy Customer'
               ELSE 'Needs Improvement'
          END AS feedback_status
   FROM cust_feedback;

The CASE statement categorizes customers as either ‘Happy’ or needing ‘Improvement’ based on their satisfaction scores.

Using CASE statements gives you a flexible way to combine data, making your results more personalized and tailored to specific conditions. It’s like having a customized assistant for your data merging tasks.

Pro Tips – Check Out

Here are a few tips that can help fix the response time to run the query.

1. Optimize for Performance: Keep your merging simple to avoid slowing down your queries. If possible, prep your data outside the query.
2. Use Consistent Separators: Stick to the same separators (like spaces or commas) for easier data understanding.
3. Handle NULL Values Well: Pick methods that deal with null values properly to avoid surprises. CONCAT() is usually safer than the plus operator.
4. Make it Readable: Write clear and short queries, even for tricky merging. Use clear names and comments for better understanding.

SQL Query Concatenate Examples

Let’s apply what we’ve learned to real-world situations:

Example 1: Merging Date and Time in MySQL

Suppose your database has separate date and time columns. You can use CONCAT() to combine them into a single date-time column.

SELECT CONCAT(date_column, ' ', time_column) AS datetime_combined
FROM your_table;

This query creates a new column named datetime_combined by merging the date_column and time_column.

Example 2: Creating Usernames in SQL Server

Imagine you have a user information database, and you want to create usernames by combining the first letter of the first name with the full last name.

SELECT CONCAT(LEFT(first_name, 1), last_name) AS username
FROM users_table;

Here, the LEFT() function takes the first letter from first_name, and CONCAT combines it with last_name to make unique usernames.

Example 3: Dynamic Email Addresses in PostgreSQL

If you need to create email addresses by combining the username and a fixed domain:

SELECT CONCAT(username, '@example.com') AS email
FROM users_data;

This query forms email addresses by merging the username with the domain ‘@example.com’.

Conclusion

By mastering SQL query merge, you gain a powerful tool for handling strings within your database. This skill opens up new possibilities for data analysis, reporting, and application development. The various methods and insights we’ve covered empower you to confidently handle any merging challenge.

Remember, practice is essential! Play around with different scenarios, explore advanced functions, and refine your skills to become skilled at string fusion within your SQL queries. Whether you’re a beginner or an experienced SQL user, the ability to merge strings is a valuable asset in your data manipulation toolkit.

Happy Learning SQL,
Team TechBeamers