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Lesson 5 — SELECT & WHERE Cheat Sheet

SQL

Key Ideas

1SELECT Basics. SQL -- All columns SELECT * FROM students; -- Specific columns SELECT name, age, grade FROM students; -- Column aliases SELECT name AS student_name, age AS years_old F...

2WHERE Comparison Operators. SQL SELECT * FROM students WHERE age = 17 ; SELECT * FROM students WHERE age != 17 ; -- or <> 17 SELECT * FROM students WHERE age > 16 ; SELECT * FROM student...

3LIKE Pattern Matching. SQL -- % = any number of characters SELECT * FROM students WHERE name LIKE 'A%' ; -- starts with A SELECT * FROM students WHERE email LIKE '%gmail%' ; -- contains gmai...

4NULL Checks and Logical Operators. SQL -- NULL checks (always use IS NULL, never = NULL) SELECT * FROM students WHERE email IS NULL ; SELECT * FROM students WHERE email IS NOT NULL ; -- AND, OR, NOT SEL...

5ORDER BY, LIMIT, DISTINCT Combined. SQL -- Sort alphabetically SELECT name, grade FROM students ORDER BY grade ASC , name ASC ; -- Top 3 oldest students SELECT name, age FROM students ORDER BY age DESC L...

Code Examples

-- All columns
SELECT * FROM students;

-- Specific columns
SELECT name, age, grade FROM students;

-- Column aliases
SELECT name AS student_name, age AS years_old FROM students;

-- Calculated column
SELECT name, age, age + 1 AS next_year_age FRO...

SELECT * FROM students WHERE age = 17;
SELECT * FROM students WHERE age != 17;    -- or <> 17
SELECT * FROM students WHERE age > 16;
SELECT * FROM students WHERE age >= 17;
SELECT * FROM students WHERE age BETWEEN 15 AND 18;  -- inclusive
S...

-- % = any number of characters
SELECT * FROM students WHERE name LIKE 'A%';       -- starts with A
SELECT * FROM students WHERE email LIKE '%gmail%'; -- contains gmail
SELECT * FROM students WHERE name LIKE '%an';      -- ends with 'an'

-- _ = exactl...