SQL Basics

Question 1

SUM() function

Answer 1

SELECT SUM(col)
FROM table;

Question 2

MIN() function

Answer 2

SELECT MIN(col)
FROM table;

Question 3

MAX() function

Answer 3

SELECT MAX(col)
FROM table;

Question 4

AVG() function

Answer 4

SELECT AVG(col)
FROM table;

Question 5

COUNT() function

Answer 5

SELECT COUNT(* or col)
FROM table;

Question 6

GROUP BY clause

Answer 6

SELECT col, COUNT(*)
FROM table
GROUP BY col;

• GROUP BY must be used with an aggregate function
• Columns in the SELECT that are not part of the aggregate function must be included in the GROUP BY clause

Question 7

HAVING clause

Answer 7

SELECT col, COUNT(*)
FROM table
GROUP BY col
HAVING COUNT(*) > 10;

• HAVING must be used with the GROUP BY clause
• Cannot use aliases in the SELECT clause

Question 8

DISTINCT clause

Answer 8

SELECT DISTINCT col
FROM table;

SELECT COUNT(DISTINCT col)
FROM table;

• Must be used with SELECT
• Can be combined with aggregate functions - typically COUNT

Question 9

Addition (operator)

Answer 9

+

Question 10

Subtraction (operator)

Answer 10

-

Question 11

Multiplication (operator)

Answer 11

*

Question 12

Division (operator)

Answer 12

/

Question 13

Modulus (operator)

Answer 13

%

Question 14

Exponention (operator)

Question 15

Negation (operator)

Answer 15

• (as a prefix, e.g. -15)

Question 16

Filter even numbers

Answer 16

WHERE col % 2 = 0

Question 17

Filter odd numbers

Answer 17

WHERE col % = 1