sql - 有加入计数

Question

我想知道哪个播放列表有超过 2 首歌曲。该语句有效，但我想要播放列表的名称和显示歌曲的 count() 。我想我必须使用连接，但我不明白这应该如何工作。有人可以帮忙吗？

playlist table
++++++++++++++
id
name

playlist_songs table
++++++++++++++++++++
song_id
playlist_id


SELECT p.name FROM playlist p 
WHERE p.id in (SELECT s.playlist_id counter FROM playlist_songs s
group by playlist_id
having count(song_id)>2);

Answer 1

我想要播放列表的名称和所显示歌曲的 count()。

这是使用谓词JOIN的优点之一：IN

SELECT 
  p.name, 
  COUNT(song_id) counter
FROM playlist p 
INNER JOIN playlist_songs s ON  p.id = s.playlist_id 
GROUP BY playlist_id
HAVING COUNT(song_id) > 2;

Answer 2

尝试：-

SELECT
  p.name,
  count(s.song_id)
FROM
  playlist p
INNER JOIN
  playlist_songs s
ON
  p.id = s.playlist_id
GROUP BY
  p.name
HAVING
  COUNT(s.song_id) >= 2

这是 SQL 服务器语法，但应该适用于 Oracle。

Answer 3

这就是你需要的：

SELECT p.name as name, count(*) as counter
FROM playlist p left outer join playlist_songs s on (p.id = s.playlist_id)
GROUP BY p.name
HAVING count(*) > 2

Answer 4

请试试：

SELECT a.name
FROM
  playlist a INNER JOIN  playlist_songs b 
  ON a.id = b.playlist_id
GROUP BY a.name
HAVING COUNT(*) >1

Answer 5

如果可能，请始终使用 join

SELECT p.name play_list,count(s.song_id) total_songs 
FROM playlist p 
INNER JOIN playlist_songs s 
ON p.id = s.playlist_id 
GROUP BY p.name 
HAVING COUNT(s.song_id) >= 2;