🔹 String Functions in SQL
These are used to manipulate text values (CHAR, VARCHAR, etc.).
1. UPPER() – Convert to uppercase
SELECT UPPER('hello world') AS UpperCase;
-- Output: HELLO WORLD
2. LOWER() – Convert to lowercase
SELECT LOWER('HELLO SQL') AS LowerCase;
-- Output: hello sql
3. LENGTH() or LEN() – Find length of string
(MySQL → LENGTH, SQL Server → LEN)
SELECT LENGTH('Database') AS StringLength;
-- Output: 8
4. SUBSTRING() – Extract part of string
SELECT SUBSTRING('Database', 1, 4) AS SubPart;
-- Output: Data
5. CONCAT() – Join strings
SELECT CONCAT('SQL', ' ', 'Tutorial') AS FullText;
-- Output: SQL Tutorial
6. TRIM() – Remove spaces
SELECT TRIM(' SQL ') AS Trimmed;
-- Output: SQL
7. REPLACE() – Replace substring
SELECT REPLACE('I like SQL', 'SQL', 'MySQL') AS UpdatedText;
-- Output: I like MySQL
🔹 Date Functions in SQL
These are used to manipulate and extract date/time values.
1. NOW() / GETDATE() – Current date & time
(MySQL → NOW(), SQL Server → GETDATE())
SELECT NOW() AS CurrentDateTime;
-- Output: 2025-08-25 14:35:10
2. CURDATE() – Current date
SELECT CURDATE() AS TodayDate;
-- Output: 2025-08-25
3. YEAR(), MONTH(), DAY() – Extract parts of date
SELECT YEAR('2025-08-25') AS YearPart,
MONTH('2025-08-25') AS MonthPart,
DAY('2025-08-25') AS DayPart;
-- Output: 2025 | 8 | 25
4. DATE_ADD() – Add interval to date
SELECT DATE_ADD('2025-08-25', INTERVAL 7 DAY) AS NextWeek;
-- Output: 2025-09-01
5. DATEDIFF() – Difference between dates
SELECT DATEDIFF('2025-12-31', '2025-08-25') AS DaysLeft;
-- Output: 128
6. DATE_FORMAT() – Format date
SELECT DATE_FORMAT('2025-08-25', '%d-%M-%Y') AS FormattedDate;
-- Output: 25-August-2025
✅ Summary
- String Functions → UPPER, LOWER, SUBSTRING, CONCAT, TRIM, REPLACE, LENGTH
- Date Functions → NOW, CURDATE, YEAR, MONTH, DAY, DATE_ADD, DATEDIFF, DATE_FORMAT