SQL查询计数问题

Question

I've two tables artist and members . artist has zero to many relation with members. (one artist may have 0 or many members)

So, I want to get all the fields of artist with the total number of members, that he has.

I write a query, but, it returns 0 count if there is no artist in the table (artist table is empty). I am using this query

SELECT a.artistname, count(m.id) as total 
    FROM artist a, members m 
    WHERE m.artist_id = a.id

It should simply not return anything if there is no artist.

Thank you!

Answer 1

I'm assuming that your field name is artistname in the artist table,

The query should go like this:

SELECT artist.artistname, COUNT(members.id) AS total_members
FROM artist
LEFT JOIN members ON members.artis_id = artist.id
GROUP BY artist.artistname

Use join, and to use sql count you need to use group by .

Answer 2

This should work:

   SELECT a.artistname, 
          count(m.id)
     FROM artist a
LEFT JOIN members m 
       ON m.artist_id = a.id;

Answer 3

Perhaps the artistname is empty. Did you check the data? You could try the following modified query:

SELECT a.artistname, count(m.id) as total 
FROM artist a, members m 
WHERE m.artist_id = a.id
AND   a.artistname is NOT NULL
AND   a.artistname <> '';