我在 SQL 数据库中有两个表，需要从一个表中获取基于分组的数据，其他正常

Question

table 1: decks

deckid	name
1662490522316	test1
1662975567468	test3
1663153348829	test4/@/4
1664289454461	Science Class EBP Physics 9th
1665037005819	d/@/dog

table 2: cards

cardid	noteid	deckid
1635883239955	1635883239955	1664289454461
1635883239956	1635883239955	1664289454461
1635883343194	1635883343194	1664289454461
1635883343195	1635883343194	1664289454461
1635883382043	1635883382043	1664289454461
1635883382044	1635883382043	1664289454461
1635883439273	1635883439273	1664289454461
1635883439274	1635883439273	1664289454461
1635883509673	1635883509673	1664289454461
1635883509674	1635883509673	1664289454461
1662490587893	1662490587892	1662490522316
1662491389237	1662491389237	1662490522316
1662491433306	1662491433306	1662490522316
1662886491604	1662886491600	1662490522316
1662886955205	1662886955203	1662490522316
1662965836930	1662965836929	1662490522316
1663129181833	1663129181832	1662975567468
1663675409308	1663675409308	1663153348829
1663675409309	1663675409308	1663153348829
1663728830758	1663728830757	1662975567468
1664353381308	1664353381307	1662490522316
1664358364077	1664358364074	1662490522316
1664358364078	1664358364075	1662490522316
1665037065057	1665037065047	1665037005819

i want a query to return deckid, name and count of cards. for each decks each deck will have n number of cards which is shown in table 2: cards

I did that with two queries 1)

SELECT decks.deckid, decks.name FROM decks

which returns

deckid	name
1662490522316	test1
1662975567468	test3
1663153348829	test4/@/4
1664289454461	Science Class EBP Physics 9th
1665037005819	d/@/dog

2)

SELECT cards.deckid, count(cards.deckid) 
FROM cards 
GROUP BY cards.deckid

which returns number(or)count of cards in one deck id

deckid	count
1662490522316	9
1662975567468	2
1663153348829	2
1664289454461	10
1665037005819	1

i am expecting a query which returns this two result in to one like.

deckid	name	count(crad.cardid)
1662490522316	test1	9
1662975567468	test3	2
1663153348829	test4/@/4	2
1664289454461	Science Class EBP Physics 9th	10
1665037005819	d/@/dog	1

Answer 1

You can link tables with JOIN if one to one, LEFT JOIN if one to many.

select d.deckid, d.name, COUNT(c.cardid) 
from
deck d 
left join cards c on c.deckid = d.deckid
group by
d.deckid, d.name

Answer 2

SELECT decks.deckid, decks.name, count(cards.cardid)
from decks
JOIN cards
ON decks.deckid = cards.deckid
GROUP BY cards.deckid

This one worked.