How can I recommend this to folks who want to learn SQL if the mathmatical operators aren't defined before questions are asked about them. It's pretty hard to google set union if you've never seen it before... I'd love some more explanation for the math.

i don't know how to write code for the given problem statement.

SELECT COUNT(*) AS number FROM ( SELECT * FROM A UNION SELECT * FROM B ) AS c

the answer is 8 you have to input the number 8 on the first line of the window else it shows an error

Gangsters You'll need to Enter the answer in Editor As well as in custom input