Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
863 views
in Technique[技术] by (71.8m points)

sql - Get count of items and their values in one column

Consider these Tables:

Table Items:

ItemID    ItemName
------------------
 1          N1
 2          N2 
 3          N4
 4          N5

and in MyTbl table I have a ItemID that may be like this:

ItemId
----
1
1
3
4
4
4

I want to write a query that return this result:

ItemId        count
-------------------
   1            2
   2            0
   3            1
   4            3

How I can do this without Cursors?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

You can select every item from Items and LEFT JOIN MyTbl on the common ItemID, counting the matches;

select 
   Items.itemId,
   count(MyTbl.itemId) as count
from Items
   left join MyTbl on (MyTbl.ItemID = Items.ItemID)
group by Items.itemId
order by Items.itemId

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...