從兩個表中選擇和計數

Question

如何使用mysqli查詢循環從兩個表中選擇和計數。

下面是表結構

table1 = categories 
id | catname 
------------- 
1 | cat1 
2 | cat2 
3 | cat3 

等。

table2 = articles 
id | article | catid 
--------------------- 
1 | art1 | 2 
2 | art2 | 2 
3 | art3 | 1 
4 | art4 | 3 

我需要這顯示像

cat 1 - 1 articles 
cat 2 - 2 articles 
cat 3 - 1 articles 

任何人都可以點我如何做到這一點使用的mysqli查詢？

Answer 1

如果你想要這個在一列中，那麼你可以使用以下命令：

select 
    concat(c.catname, ' - ', a.Total, ' articles') list 
from categories c 
inner join 
(
    select count(*) Total, 
    catid 
    from articles 
    group by catid 
) a 
    on c.id = a.catid 

見SQL Fiddle with Demo

或者你也可以做到這一點沒有子查詢：

select 
    concat(c.catname, ' - ', count(*), ' articles') list 
from categories c 
inner join articles a 
    on c.id = a.catid 
group by c.catname; 

請參閱SQL Fiddle with Demo。其結果是：

|    LIST | 
--------------------- 
| cat1 - 1 articles | 
| cat2 - 2 articles | 
| cat3 - 1 articles | 

Answer 2

試試這個

SELECT 
    c.catname, 
    COUNT(*) 
FROM categories c 
INNER JOIN articles a 
    ON c.id = a.catid 
GROUP BY 
    c.catname 

Answer 3

試試這個：

SELECT CONCAT(C.catname, ' - ', A.articles, ' Articles') 
FROM categories C 
     INNER JOIN articles A 
     ON C.id = A.catid 
GROUP BY A.catid 
ORDER BY C.catname