#1

SELECT LEFT('MySQL LEFT', 5);

#2

SELECT LEFT('MySQL LEFT', 9999);

#3

SELECT LEFT('MySQL LEFT', NULL);

#4

SELECT 
    productname, LEFT(productDescription, 50) summary
FROM
    products;

#5

SELECT 
    LEFT(productdescription, 50)
FROM
    products;

#6

SELECT 
    REVERSE(LEFT(productdescription, 50))
FROM
    products;

#7

SELECT 
    LOCATE(' ',REVERSE(LEFT(productdescription, 50))) first_space_pos
FROM
    products;

#8

SELECT
    IFNULL(NULLIF(LOCATE(' ', REVERSE(LEFT(productDescription, 50))), 0) - 1, 0)
FROM
    products;

#9

SELECT
	productDescription,
	(50 - IFNULL(NULLIF(LOCATE(' ', REVERSE(LEFT(productDescription, 50))), 0) - 1, 0)) last_space_pos
FROM
    products;

#10

SELECT 
    productDescription, LEFT(productDescription, last_space_pos)
FROM
    (SELECT 
        productDescription,
            (50 - IFNULL(NULLIF(LOCATE(' ', REVERSE(LEFT(productDescription, 50))), 0) - 1, 0)) last_space_pos
    FROM
        products) AS t;