String Functions
Manipulate text data in queries
String functions help you search, transform, and format text data.
Common String Functions
| Function | Example | Result |
|---|---|---|
| UPPER() | UPPER('hello') | 'HELLO' |
| LOWER() | LOWER('HELLO') | 'hello' |
| LENGTH() | LENGTH('hello') | 5 |
| TRIM() | TRIM(' hi ') | 'hi' |
| SUBSTR() | SUBSTR('hello', 1, 3) | 'hel' |
| REPLACE() | REPLACE('hello', 'l', 'L') | 'heLLo' |
String Concatenation
-- SQLite / PostgreSQL
SELECT first_name || ' ' || last_name AS full_name FROM users;
-- MySQL
SELECT CONCAT(first_name, ' ', last_name) AS full_name FROM users;
-- Handle NULL (PostgreSQL)
SELECT CONCAT_WS(' ', first_name, middle_name, last_name) FROM users;Practical Examples
-- Clean up data
SELECT TRIM(LOWER(email)) AS clean_email FROM users;
-- Extract domain from email
SELECT SUBSTR(email, INSTR(email, '@') + 1) AS domain FROM users;
-- Format phone number
SELECT
'(' || SUBSTR(phone, 1, 3) || ') ' ||
SUBSTR(phone, 4, 3) || '-' ||
SUBSTR(phone, 7, 4) AS formatted_phone
FROM users;