Summary  
This chapter introduces string functions in SQL for transforming, analyzing, and extracting text, demonstrating operations like case conversion, length calculation, concatenation, substring extraction, and nesting functions for advanced text processing.  

General domain of usage  
Customer data management

Functions are essential in data analysis because they let you transform, clean, and extract value from your data efficiently. In this module, you will focus on the most important SQL functions for working with text, so you can handle real-world data challenges with confidence.

Note

When working with text data in SQL, **string functions** are essential tools that let you transform, analyze, and extract information from character fields. These functions help you clean up messy data, standardize text formats, and create new values based on existing information. Whether you need to change the case of names, count the number of characters in an email address, or build custom strings for reports, string functions make these tasks simple and efficient.

-- Transform and analyze customer names using string functions
SELECT
  name,
  UPPER(name) AS name_uppercase,
  LOWER(name) AS name_lowercase,
  LENGTH(name) AS name_length
FROM customers;

You can combine multiple **string functions** in a single query to perform advanced text processing. For instance, you might want to convert a name to lowercase and then count its characters, or standardize email addresses by joining different pieces of data together. By nesting and chaining functions, you gain powerful ways to reshape and analyze your text data directly within SQL.

-- Create custom email usernames by combining and extracting strings
SELECT
  name,
  CONCAT(LOWER(SUBSTRING(name, 1, 1)), LOWER(SUBSTRING(name, POSITION(' ' IN name) + 1, 5))) AS custom_username
FROM customers;

Which function changes all characters in a string to uppercase?

Which SQL function extracts a substring from a given string?

This beginner course focuses on the essential SQL functions used for data cleaning and transformation. Learners will practice handling missing values, formatting and standardizing data, and applying string, date, numeric, logical, and null handling functions to prepare datasets for analysis. The course provides hands-on challenges directly related to the most common data preparation tasks in SQL.

Introduction to String Functions

1. Which function changes all characters in a string to uppercase?

2. Which SQL function extracts a substring from a given string?

3. Fill in the blanks to select the length of each customer's name after converting it to lowercase.