SQL : SQL query to fetch the corresponding data

Question

So, the problem is that I need to find the the total number of gifts received by the people with the nationality 'America', Now I have 2 different tables named gift_info and users_info , the users_info table contains the nationality attribute while the gift_info contains the gift_id attribute.

I have come up with something like

SELECT users_info.user_id, gift_info.gift_id, users_info.nationality
FROM gift_info
LEFT JOIN users_info
ON  gift_info.gift_id = users_info.user_id
where users_info.nationality = 'America'

the output this query gives is the user_id, the gift_id and the nationalities 'America' while I need the the total number of gifts recived by people of nationality 'America'.

Answer 1

Modify the SELECT statement to Count the number of gift IDs and add a GROUP BY clause:

SELECT COUNT(DISTINCT gift_info.gift_id)
FROM gift_info
LEFT JOIN users_info
ON  gift_info.user_id= users_info.user_id    
where users_info.nationality = 'America'
GROUP BY users_info.nationality = 'America'

Edited WHERE clause per @Sujitmohanty30's comment

Answer 2

If I understand correctly, I think you want:

SELECT COUNT(*)
FROM gift_info gi JOIN
     users_info ui
     ON gi.user_id = ui.user_id
WHERE ui.nationality = 'America';

Notes:

• An outer join is not appropriate because you need the nationality.
• Table aliases make the query easier to write and to read.
• I think a simple COUNT(*) suffices to get the number of gives. If you want the number of people, use COUNT(DISTINCT ui.user_id) .