SQL String Functions: 10 of the Most Useful

Learn how you can manipulate text strings on the database server rather than in your core app.

SQL (Structured Query Language) has many built-in functions. Some of the widely-used ones are string functions.

Strings are a data type used to store character-based information. SQL string functions are pre-defined functions. You can use them to manipulate string values and perform various database operations.

String functions process and return results which may be strings or numeric values. You will use the following standard string functions when working with SQL.

CONCAT() is a widely used function in SQL servers. You will use it to join two or more strings into a single string. The function takes strings as inputs and concatenates them to a single-string value. It accepts the strings and the separator as arguments.

The syntax is:

See the following example:

Which will return the value, "MakeUseOfwebsite".

The SELECT statement is one of the most commonly used SQL commands. You will use it to access the records from database tables.

You can retrieve selected data according to the conditions specified in the function. You can also use other statements like ORDER BY, WHERE, GROUP BY, etc., to manipulate databases.

Another form of the CONCAT() function is the CONCAT_WS(). This function takes strings as inputs and concatenates them into a single string. But it puts a separator between them. The separator is usually the first argument.

For example:

The return value will be "MakeUseOf, website".

The SUBSTRING() function returns part of a string starting from the stated position. It takes three arguments the string, start, and length. The length is optional.

The syntax:

The start position starts at index one (not index zero, as in some programming languages). The length (len) indicates the number of characters to extract. The length must always be a positive number.

For example:

Returns the value "cd".

The SQL LENGTH() function gives the length of the string. It takes the string as an argument. The syntax is:

For example, to find the length of the name 'Jones', you will write the function as so:

The return value is 5.

This function changes all the characters in a string to uppercase. It's also known as UCASE() in some databases. The syntax is:

For example, convert the sentence "I love SQL tutorials." to uppercase.

The return value is "I LOVE SQL TUTORIALS!"

SQL also has a LOWER() function. This function converts strings into lowercase, the opposite of the UPPER() function.

The TRIM() function removes spaces surrounding a string. It takes the string as an argument. The syntax is:

For example:

The return value will be "abcd".

You can also use TRIM() to remove other characters from a string with the following syntax:

The function includes arguments mentioning where it should act. For example, BOTH refers to both prefixes and suffixes of the string. While LEADING refers to the prefix and TRAILING to the suffix, respectively. The part of the string removed is also included [remstr].

For example:

Returns "bcdaaa".

You can also use the RTRIM() function to remove characters from the right side of the string, and LTRIM() to remove characters from the left.

The REPLACE() function replaces a substring in a string with a new substring. The syntax :

The original_string is the input string in which you want to perform replacements. The substring_to_replace is the substring you are replacing in the original_string. And the new_substring is the string you are placing in the original_string.

For example:

The result will be "MICROSOFT".

Use the INSTR() function to find the starting position of a substring within a string. It works similar to the CHARINDEX() function in Oracle servers. Or the general POSITION() function used in PostgreSQL databases.

The Syntax is:

The string is the original string you want to find the substring. The substring is what you are looking for in the string. The start_position (optional) is where you begin. If it's not specified, the search starts from the beginning of the string.

The occurrence (optional) is of the substring you want to find. If the occurrence is not specified, the function returns the first occurrence. The function performs case-insensitive searches.

For example:

The result will be 2.

This function returns the rightmost characters of the string. It includes the string and the length (len) of characters to return as arguments.

The syntax is:

For example:

The return value is "def".

SQL also has the LEFT() function that does the opposite of the RIGHT()function. It returns gives the first left characters of the string.

The syntax:

For example:

The result will be "Micro".

You can use the INSERT() function to change a string by inserting a new string. You can also specify the length and position to add the string, but these are optional arguments. You can also insert records into database tables using SQL.

The syntax is:

The string is the original string you want to insert. The position is where you would want to insert the new _string. The length is the number of characters to replace, and the new_string is the string to insert.

For the below SQL

The result is "abcdefgIJKL"

Use the REPEAT() function to multiply a string according to a desired number. The syntax is:

The function takes the string and the number of times to repeat as arguments. For example:

The result is "MUOMUOMUO."

SQL provides various functions and operators to work with strings; these are just the most common.

If you work with relational databases, learning SQL string functions is essential. Knowledge of these functions will help you manipulate and store data efficiently.

You will effectively perform data cleaning, formatting, and extraction. You will also master string comparison, sorting, and pattern matching. These are essential skills today in business performance optimization.

Sandra is a Tech enthusiast with a background in Journalism and Full-stack web development. She specializes in web development and Cloud technology. For leisure, Sandra enjoys a good thriller, reading, and hiking.