當值之一是SELECT語句的結果時，如何使用COUNT（DISTINCT…）？

Question

我有一條返回行的SQL語句：

SELECT DISTINCT wp_w2bw2c_event.venue_id, 
    (SELECT MIN(begin_date)     
        FROM wp_w2bw2c_event_detail 
        WHERE wp_w2bw2c_event_detail.event_id = wp_w2bw2c_event.id) 
    as begin_date, 
    wp_w2bw2c_event.id as event_id 
    FROM wp_w2bw2c_event 
    INNER JOIN wp_w2bw2c_venue 
    ON wp_w2bw2c_venue.id = wp_w2bw2c_event.venue_id 
    INNER JOIN wp_w2bw2c_event_detail 
    ON wp_w2bw2c_event_detail.event_id = wp_w2bw2c_event.id 
    WHERE wp_w2bw2c_venue.venue_name LIKE '%ironworks%' 
    OR artist_name LIKE '%ironworks%' 
    OR event_title LIKE '%ironworks%' 
    OR event_detail_title LIKE '%ironworks%' 
    ORDER BY wp_w2bw2c_event.venue_id, begin_date, event_id 

如果嘗試使用COUNT函數僅計算行數，則會收到SQL數據庫錯誤

SELECT COUNT(DISTINCT wp_w2bw2c_event.venue_id, 
    (SELECT MIN(begin_date)     
        FROM wp_w2bw2c_event_detail 
        WHERE wp_w2bw2c_event_detail.event_id = wp_w2bw2c_event.id) 
    as begin_date, 
    wp_w2bw2c_event.id as event_id) 
    FROM wp_w2bw2c_event 
    INNER JOIN wp_w2bw2c_venue 
    ON wp_w2bw2c_venue.id = wp_w2bw2c_event.venue_id 
    INNER JOIN wp_w2bw2c_event_detail 
    ON wp_w2bw2c_event_detail.event_id = wp_w2bw2c_event.id 
    WHERE wp_w2bw2c_venue.venue_name LIKE '%ironworks%' 
    OR artist_name LIKE '%ironworks%' 
    OR event_title LIKE '%ironworks%' 
    OR event_detail_title LIKE '%ironworks%' 

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'as begin_date, 
    wp_w2bw2c_event.id as event_id 
    FROM wp_w2bw2c_event 
    INNE' at line 5

如何更改SQL，以便COUNT(DISTINCT...與SELECT的結果一起使用？

Answer 1

您的查詢返回不同的行。 因此，您要做的就是計算該查詢的結果：

select count(*) from (your query) q;

Answer 2

您嘗試的操作不必要地復雜。 簡單方法有什么問題？

select venueId
, min(begin_date) minBeginDate
from etc
where whatever
group by venueId

這將為您提供獨特的價值。