LIMIT在mysql子查詢

Question

我有一個MySQL語句的問題。

我有這樣的：

SELECT ad.*, 
    (SELECT img.image 
    FROM '.$this->config->db_prefix.'_images AS img 
    WHERE img.aid = ad.aid LIMIT 1) AS img 
FROM '.$this->config->db_prefix.'_adverts ad 
WHERE fid = :fid 
ORDER BY cr_date DESC 

，工作正常，但我需要從_images表中獲取的所有圖像，所以如果我刪除LIMIT 1我得到

Cardinality violation: 1242 Subquery returns more than 1 row 

結果從SQL是輸出爲JSON。

Answer 1

您可以使用MySQL的GROUP_CONCAT()聚合函數：

SELECT ad.*, (SELECT GROUP_CONCAT(img.image) FROM '.$this->config->db_prefix.'_images AS img WHERE img.aid = ad.aid) AS img FROM '.$this->config->db_prefix.'_adverts ad WHERE fid = :fid ORDER BY cr_date DESC 

再後來explode()它在PHP或split()它的JavaScript。

Answer 2

你遇到的問題是，當你說select時，mysql希望一次只能得到一個條目。看看mysql JOIN語句。

http://dev.mysql.com/doc/refman/5.0/en/join.html

select ad.*, img.image 
from TABLE1 ad 
JOIN TABLE2 img on ad.aid = img.aid 
WHERE CONDITION 
ORDER BY cr_date DESC.