Adventures in Machine Learning

Unlock Your SQL String Manipulation Potential with These Essential Functions

Get the Most Out of SQL: A Guide to String Functions

As a SQL developer, you know that manipulating strings is an essential part of database management. You have to know how to slice, concatenate, split, and compare strings.

You also have to know how to make your code readable, manageable, and efficient. Understanding string functions is essential to all of this.

In this article, we will explore some of the most important SQL string functions and their benefits. We will give you examples of how these functions work in practice.

By the end of this article, you will have a better understanding of SQL string functions and how to use them to your advantage.

SQL String Functions for Manipulating Strings

Concatenate Strings With CONCAT

Often, you need to merge two or more strings into one. Instead of writing multiple columns, you can use CONCAT to do it for you.

CONCAT is a handy SQL string function which concatenates two or more strings to produce a single string output. For instance, suppose you have two columns, first_name and last_name, in a table.

You can use CONCAT to combine them into a full name column. SELECT CONCAT(first_name, ‘ ‘, last_name) AS full_name

FROM users;

This SQL code will output a new column named full_name which will contain the combination of both first and last name in separate strings.

Replace Strings With REPLACE

Suppose you have to update numerous records in your database, and you need to make the same change for all of them. Or maybe you need to remove a particular character or word from some strings.

Instead of manually updating each record, you can use the REPLACE SQL function to make the changes. For instance, if you want to replace all the occurrences of the word ‘female’ with the word ‘woman,’ you can write the below code.

UPDATE users

SET gender = REPLACE(gender, ‘female’, ‘woman’);

This will replace all the appearances of the word ‘female’ in the gender column with ‘woman’ for all users in the table.

Get Substrings With SUBSTR

The SUBSTR SQL function allows you to extract a part of a string from a particular position. You can specify the start position and the number of characters you want to extract using SUBSTR.

For instance, if you want to extract the first three letters of a string column named ‘color,’ you can write the following code:

SELECT SUBSTR(color, 1, 3) AS short_color FROM products;

This code will give you a new column named ‘short_color’ in the ‘products’ table which will contain the first three characters of the existing ‘color’ column.

Get ASCII Code and Character With ASCII and CHR

The ASCII SQL function gives the ASCII/Unicode code of a particular character, while CHR does the opposite- producing the character corresponding to a specified ASCII/Unicode code. For instance, you can use these functions to convert all characters to their corresponding ASCII codes or vice versa.

SELECT customer, ASCII(customer) as ascii_code FROM orders;

The SQL code above will generate a new column in the ‘orders’ table named ‘ascii_code’ containing the ASCII code for the corresponding characters in the ‘customer’ column.

Remove Unnecessary Characters With TRIM

Sometimes, you might need to remove spaces located at the beginning, end, or both ends of a string value. In such cases, the TRIM SQL function comes in handy.

TRIM removes characters based on their location in the string.

Useful SQL String Functions for Developers

Knowing SQL string functions is indispensable for database developers to work efficiently and effectively. SQL string functions improve code comprehension, making its execution quicker, and optimize performance.

For example:

Readable Outputs

Concatenating columns and converting values to specific formats with SQL string functions can make outputs clearer. This makes it easier for all involved parties to understand the data presented, instead of relying on guesswork to decipher the information.

Updating Records

One benefit of SQL string functions, such as REPLACE and TRIM, is that they can make updating records a faster process. These functions optimize performance by allowing developers to manipulate strings without incurring extended downtime to the database.

Adding Characters to IDs

SQL string functions make it easier for developers to add prefixes or suffixes to specific columns in existing tables. Instead of manually inserting a prefix/suffix column and migrating data across tables, developers can use SQL string functions to update the existing IDs quickly.


In todays fast-paced digital world, optimizing your code is an integral part of a developer’s work. A thorough understanding of SQL string functions can help with code effectiveness, optimizing database performance, and making outputs much more readable.

In this guide, weve examined some of the most vital SQL string functions for manipulating strings, and their benefits. With this knowledge, you can work faster and more efficiently, thus optimizing your workflow and enhancing your productivity.

3) CONCAT Function in Detail

SQL CONCAT function is an essential string manipulation function that allows you to combine two or more strings to form a single string. This function is useful in SQL to merge the data from different columns into a single column to produce more readable, manageable, and informative output.

CONCAT function has excellent usability potential as it can be used across different data types like integers, decimals, or alphanumeric characters.

Syntax and Usage

The syntax for CONCAT function in SQL is as follows:

CONCAT(entry_char1, entry_char2, ……, entry_charN)

The CONCAT function takes an indefinite number of string inputs separated by commas, depending on the requirement for combining strings. You can combine two strings or more using a comma-separated list of the entry characters as arguments.

The arguments can be constants, column names, or variables. For instance, the following code snippet merges the First Name and Last Name columns in the ‘users’ table to form a new column named Full Name:

SELECT CONCAT(First_Name, ‘ ‘, Last_Name) AS ‘Full_Name’ FROM users;

Here, the CONCAT function merges the ‘First_Name’ column with a space between it and the ‘Last_Name’ column to form a new column named ‘Full_Name.’

Examples of CONCAT Function in Use

The CONCAT function finds its application in a wide range of industries, from data analysis to software development. Here are some specific examples of how to put a SQL CONCAT function to practical use.

Combining Strings

A SQL CONCAT function is an easy tool for combining strings. In the case of joining multiple values using a separator, the CONCAT_WS function is useful.

However, CONCAT is used to merge two or more strings. For instance, assume there is a table named ‘inventory’ with columns for ‘product’ and ‘color’.

The following code combines these two columns into a new column named “Inventory” :

SELECT CONCAT(product, ‘ – ‘, color) AS ‘Inventory’ FROM inventory;

Here, CONCAT is used to merge the ‘product’ and ‘color’ columns with a hyphen (-) between them.

Readable Output

When working with databases, readability plays an important role. When joining strings in SQL, syntax and spacing are essential for clear and comprehensible output.

The CONCAT function can be used to arrange strings in a readable format to make it easier for data analysts to interpret the output quickly. For instance, assume that you have a table with time as a string in two different columns: ‘hour’ and ‘minute,’ respectively – the following code merges these columns to form a single column for the display of time:

SELECT CONCAT(hour, ‘:’, minute) AS ‘Time’ FROM time_table;

Here, the CONCAT function is used to merge the ‘hour’ and ‘minute’ columns with a colon “:” in between them.

4) REPLACE Function in Detail

SQL REPLACE function is a handy string manipulation function that allows you to replace a specific set of characters in a string with a new set of characters. This function is especially useful in SQL when dealing with string manipulation tasks that involve string searching and string replacement.

The REPLACE function is often used to update table records, where specific values need replacement with new ones.

Syntax and Usage

The syntax for REPLACE function in SQL is as follows:

REPLACE(string, entry_char, replace_with)

Here, string implies the string that needs replacing. The entry_char implies the string that needs replacing, whereas the replace_with implies the character string that will replace the entry_char in the string.

For instance, the code snippet below will replace the “old_name” in column “users_name” with the “new_name”:

UPDATE Users SET Users_Name = REPLACE(Users_Name, ‘old_name’, ‘new_name’);

Here, the REPLACE function will look for the “old_name” string occurrences in the “Users_Name” column of the “Users” table and replace them with the “new_name” string.

Examples of REPLACE Function in Use

After understanding the syntax of the REPLACE function, it is essential to know how to put it to practical use. Below are some examples of how to apply the REPLACE function in SQL in various scenarios.

Updating Records

SQL REPLACE function is useful when the database administrator needs to update a table record. With the REPLACE function, instead of updating data row by row, the administrator can use SQL to affect the desired changes across the table efficiently.

For example, imagine that the Sales Manager has left the company, and you need to replace his name with the name of the new Sales Manager. You can use the REPLACE function in SQL to execute a mass update in one command:

UPDATE employees

SET name = REPLACE(name, ‘Sales Manager XY’, ‘Sales Manager AB’)

WHERE position = ‘sales’;

In this code, the REPLACE function will modify all instances of ‘Sales Manager XY’ in the ‘name’ column and replace them with ‘Sales Manager AB’, only for employees who had the position of ‘Sales.’


SQL String functions, particularly CONCAT and REPLACE, are essential tools for SQL developers to manage strings. With these functions, developers can manipulate string data to their liking, making their code more readable, efficient, and easier to scale.

Additionally, the flexibility and functionality of these functions make them beneficial across a wide range of industries. By taking the time to understand and incorporate these functions, SQL developers enhance their workflow and overall productivity.

5) SUBSTR Function in Detail

The SUBSTR function in SQL stands for substring function, which is used to retrieve a part of a string. The substring is a smaller part of a bigger string or an entire string.

The SUBSTR function helps in manipulating strings by extracting specific parts of a string based on the position and length parameter specified. In SQL, the SUBSTR function is used to create substrings from columns in a table.

Syntax and Usage

The syntax for the SUBSTR function in SQL is as follows:

SUBSTR(char, position, length)

Here, char implies the string that the function will extract the substring from, position implies the starting position of the character or substring that the function should retrieve, and length implies the length of the substring required. For example, the following code retrieves a substring from the string, ‘SQL Query’ and returns ‘Q’:


Here, the substring function retrieves a substring from the ‘SQL Query’ string, starting from the 5th position, which is ‘Q.’

Examples of SUBSTR Function in Use

SQL developers can use the SUBSTR function in SQL to create substrings when dealing with specific data types such as names, phone numbers, and reference numbers among others.

Creating Substrings

The ability to extract a part of a string with the SUBSTR function is advantageous when working with specific data types, such as names, where the first and last names are required as separate columns in a table. For instance, consider a table named ‘users,’ where you need to extract the first three characters from the ‘last_name’ column:

SELECT SUBSTR(last_name, 1, 3)FROM users;

Here, you can acquire a new column named ‘short_last_name’ that contains the first three characters from the ‘last_name’ column in the ‘users’ table.

Updating Records

SQL developers can use the SUBSTR function to update records in a table with specific substrings that need to be replaced with new substrings. For example, let’s assume a company wants to change the phone number format from 123-456-7890 to (123)-456-7890.

You can use SUBSTR to make the change efficiently:

UPDATE company_phone_book SET phone_number = CONCAT(‘(‘, SUBSTR(phone_number, 1, 3), ‘)-‘, SUBSTR(phone_number, 4, 3), ‘-‘, SUBSTR(phone_number, 7, 4));

Here, you will update the ‘phone_number’ column in the ‘company_phone_book’ table and replace the first substring, which represents the area code, with a substring that has a format in parentheses-‘(123)-456-7890.’

6) ASCII and CHR Functions in Detail

The ASCII and CHR functions are SQL string functions that convert character and numeric data to a corresponding ASCII code and vice versa. These functions are useful in retrieving ASCII code, which is essential in character manipulation in SQL queries, and also the character that corresponds to a specified ASCII code.

Syntax and Usage

The ASCII function in SQL is used to retrieve the ASCII code of the first character of a given string. The ASCII code for a character is a number that represents the character.

The syntax of the ASCII function is as follows:


Here, ‘char’ is a string whose first character’s ASCII code the function will compute. For instance, the following code returns the ASCII code for the first character in the ‘sql’ string :


Here, the function returns 115, which is the ASCII code for the letter ‘s.’

The CHR function in SQL, on the other hand, is used to convert a specified ASCII code into its corresponding character.

The syntax for CHR function is as follows:


Here, ‘code’ represents the ASCII code that corresponds to the character that the function will return. For instance, the following code returns the character corresponding to ASCII code 97, which is the letter ‘a’:

SELECT CHR(97) AS character;

Here, the function returns ‘a’ as the corresponding character for ASCII code 97.

Examples of ASCII and CHR Functions in Use

The ASCII and CHR functions can be useful for performing manipulations in SQL queries on character data.

Finding Records

The ASCII function can be used to search for particular sections of a string. Assume that you want to find a record that contains a specific letter.

Knowing the ASCII code can help make finding this record more efficient. For instance, if you have a table called ’employee_names’ that contains employees’ first and last names, you can use the following code to find employees whose first names start with the letter ‘C’:

SELECT * FROM employee_names WHERE ASCII(LEFT(first_name, 1)) = 67

Here, the ASCII function is used to convert the first character of the first name to an ASCII code.

The code for the ‘C’ character is 67. Using this code and a WHERE statement, you can filter out all the records for which the first character of the first name is not ‘C.’


SQL string functions help developers to manipulate string data, which is a fundamental practice when working with databases. The SUBSTR function is useful in pulling substrings from a string, while the ASCII and CHR functions are helpful in finding specific sections of a string and converting between characters and their ASCII codes.

By leveraging these functions in SQL queries, developers can manipulate strings more efficiently, making their code more readable and easier to maintain.

7) TRIM Function in Detail

In SQL, the TRIM function is used to remove certain characters from either the end or both the beginning and end of a string. The characters are specified as arguments and can be spaces or specific characters.

The TRIM function not only makes database management and data analysis more straightforward but also makes strings much more manageable, readable, and effective.

Syntax and Usage

The syntax for TRIM function in SQL is as follows :

TRIM([LEADING | TRAILING | BOTH] [edit_char FROM] value)

In the syntax, edit_char refers to the characters to be removed from the string, while value is the string or column from which the characters are to be removed. LEADING, TRAILING, and BOTH are optional parameters that determine from where to remove the specified character(s).

LEADING removes the characters from the beginning of the string. TRAILING removes the characters from the end of the string.

BOTH removes the specified characters from both the beginning and end of the string. For example, consider a column named ‘name’