SELECT — Data Read करणे

-- सगळे columns, सगळ्या rows
SELECT * FROM students;

-- फक्त specific columns
SELECT name, city, marks FROM students;

-- Column ला alias (नवे नाव)
SELECT name AS student_name, marks AS score
FROM students;

-- Calculations columns मध्ये
SELECT name, marks, marks * 0.1 AS bonus
FROM students;

-- DISTINCT — unique values फक्त
SELECT DISTINCT city FROM students;
-- Pune, Mumbai, Nagpur, Nashik (duplicates remove)

-- Ascending order (default)
SELECT name, marks FROM students ORDER BY marks ASC;

-- Descending — top scorers आधी
SELECT name, marks FROM students ORDER BY marks DESC;

-- Multiple columns ने sort
SELECT name, city, marks
FROM students
ORDER BY city ASC, marks DESC;

-- LIMIT — फक्त n rows
SELECT name, marks FROM students
ORDER BY marks DESC
LIMIT 3;  -- Top 3 students

-- LIMIT with OFFSET — pagination साठी
SELECT name FROM students
ORDER BY id
LIMIT 5 OFFSET 10;  -- 11 ते 15 rows (page 3)

-- NULL values असलेल्या rows शोधणे
SELECT name, email FROM students
WHERE email IS NULL;

-- NULL नसलेल्या rows
SELECT name, email FROM students
WHERE email IS NOT NULL;

-- COALESCE — NULL असेल तर default दाखवा
SELECT name, COALESCE(email, 'No Email') AS contact
FROM students;

-- IFNULL (MySQL) — same as COALESCE for 2 args
SELECT name, IFNULL(city, 'Unknown') AS city
FROM students;