#1

SELECT 
    lastname
FROM
    employees
ORDER BY lastname;

#2

SELECT DISTINCT
    lastname
FROM
    employees
ORDER BY lastname;

#3

SELECT DISTINCT
    state
FROM
    customers;

#4

SELECT DISTINCT
    state, city
FROM
    customers
WHERE
    state IS NOT NULL
ORDER BY state , city;

#5

SELECT 
    state, city
FROM
    customers
WHERE
    state IS NOT NULL
ORDER BY state , city;

#6

SELECT 
    state
FROM
    customers
GROUP BY state;

#7

SELECT DISTINCT
    state
FROM
    customers;

#8

SELECT DISTINCT
    state
FROM
    customers
ORDER BY state;

#9

SELECT 
    COUNT(DISTINCT state)
FROM
    customers
WHERE
    country = 'USA';

#10

SELECT DISTINCT
    state
FROM
    customers
WHERE
    state IS NOT NULL
LIMIT 5;