String Functions

SQL provides a set of built-in string functions for manipulating text data directly within a query - useful for cleaning, formatting, and extracting information from text columns.

Common String Functions

• UPPER() / LOWER() - convert text to uppercase or lowercase
• LENGTH() - returns the number of characters in a string
• TRIM() - removes leading and trailing whitespace
• CONCAT() - joins two or more strings together
• SUBSTRING() - extracts a portion of a string
• REPLACE() - replaces occurrences of a substring with another string

Examples

-- Full name from first and last name
SELECT CONCAT(first_name, ' ', last_name) AS full_name
FROM customers;

-- Standardize case for comparison
SELECT * FROM customers WHERE LOWER(city) = 'noida';

-- Extract the first 3 characters of a product code
SELECT SUBSTRING(product_code, 1, 3) FROM products;

-- Clean up stray whitespace
SELECT TRIM(first_name) FROM customers;