[英]Select from one table and count from another
我想知道如何使用一個查詢從一個表中進行選擇並從另一個表(循環)中進行計數
餐桌雜物
------------------------------
cat_id | cat_name | parent_id
------------------------------
1 | General | 0
------------------------------
2 | News | 0
------------------------------
3 | Sports | 1
------------------------------
4 | Test | 0
------------------------------
表帖子
--------------------------------------
post_id| title | c_id | active
--------------------------------------
1 | test | 1 | 1
--------------------------------------
1 | test 1 | 2 | 0
--------------------------------------
1 | test 2 | 1 | 1
--------------------------------------
1 | Test 3 | 3 | 1
--------------------------------------
我想要顯示類別where parent_id=0
(主要類別),其前面是帖子數( where active = 1
帖子)
例如:一般(2個帖子)
誰能給我一個例子,如何用一個查詢
SELECT
`cat_name`,
(SELECT COUNT(*) FROM `posts` p WHERE p.active =1 AND p.c_id = c.cat_id) as post_count
FROM `category` c
WHERE c.parent_id = 0
ORDER BY `cat_name` ASC
嘗試此查詢,您可以在查詢中將子查詢與select語句一起使用。
select cat_name,
(select count(*)
from post
where active=1
and c_id=cat_id
) as countpost
from ctagories
where parent_id=0;
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.