SQL：计算每个类别中的项目

Question

SELECT items.id, 
       items.category, 
       COUNT(*) 
  FROM items 
 GROUP BY items.id, 
          items.category 

I want to display how many items in each category. For example,
category 1 - 6
category 2 - 7
category 3 - 4 ...
Please help me! I try this request and show me all the items with category :/

Answer 1

Try this...

SELECT items.category, 
       COUNT(*) AS Count 
FROM   items 
GROUP  BY items.category 

Answer 2

If, you want to display count based of category then use group by clause with colum category

SELECT category, count(*) as Noofitems
FROM items i
GROUP BY category; 

Tiny word of advice :- Use table alise that could be easy to follow and read/wrire

Answer 3

尝试这个...

select items.category,COUNT(items.COUNT(*)) from items Group By items.category;

Answer 4

Please use 'distinct'

SELECT distinct items.category, 
       COUNT(*) AS Count 
FROM   items 
GROUP  BY items.category

to get the correct count for each unique category